Microelectromechanical system with stiff coupling

ABSTRACT

A microelectromechanical system is disclosed that uses a stiff tether between an actuator assembly and a lever that is interconnected with an appropriate substrate such that a first end of the lever may move relative to the substrate, depending upon the direction of motion of the actuator assembly. Any appropriate load may be interconnected with the lever, including a mirror for any optical application.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This patent application is a divisional of, and claims priorityunder 35 U.S.C. §120 to, U.S. patent application Ser. No. 10/099,464,that is entitled “MICROELECTROMECHANICAL SYSTEM WITH STIFF COUPLING,”and that was filed on Mar. 14, 2002, the entire disclosure of which isincorporated by reference in its entirety herein.

FIELD OF THE INVENTION

[0002] The present invention relates to the field ofmicroelectromechanical systems and, more particularly to amicroelectromechanical system that uses a stiff coupling between anactuator assembly and a load.

BACKGROUND OF THE INVENTION

[0003] Microelectromechanical (MEM) systems are getting a significantamount of attention in the field of optical switches. MEM technologygenerally involves the fabrication of small mechanical devices on asilicon substrate, together with electronic circuitry for actuatingmotion of the mechanical device. Surface micromachining is one type offabrication technique for MEM systems. Surface micromachining generallyentails depositing alternate layers of structural material andsacrificial material on an appropriate substrate, such as a siliconwafer, which functions as a foundation for the resultingmicrostructures. Various patterning operations may be executed on one ormore of these layers before the next layer is deposited so as to definethe desired microstructures. After the microstructures have been definedin this general manner, the various sacrificial layers are removed byexposing the microstructures and the various sacrificial layers to oneor more etchants which “releases” the resulting microstructures from thesubstrate (e.g., to allow relative movement).

[0004] A MEM-based optical system may include multiple mirrormicrostructures formed on a substrate for making optical connections.Each mirror microstructure may be interconnected with at least one liftassembly, one or more actuators, and one or more displacementmultipliers. The lift assembly may be used to raise the mirrormicrostructure above the plane of the substrate and/or tilt the mirrorinto an appropriate position to provide a desired optical function. Theactuators are attached to the substrate so as to be movable relativethereto, and provide the motive force/displacement that is used toraise/tilt these mirrors. Electrostatic actuators are commonly used inthese types of systems. These types of actuators produce a short strokedisplacement which may be insufficient to raise/tilt the mirror to adesired level in at least certain instances. Therefore, the noteddisplacement multiplier(s) is typically disposed between the actuatorand its associated lift assembly to increase the displacement providedby the actuator to the lift assembly, and to thereby allow the mirrormicrostructure to be raised/tilted to a desired degree. One example of adisplacement multiplier is disclosed in U.S. Pat. No. 6,175,170.

[0005] Displacement multipliers may be designed to produce a relativelylarge output based upon a relatively small input. However, displacementmultipliers can become rather intricate, which increases developmentcosts. Moreover, displacement multipliers often require a significantamount of space on a die. Since there is only a fixed amount of spacewithin a die for fabrication of the microelectromechanical system, theuse of one or more displacement multipliers may reduce the mirrordensity within the die. Although this may be acceptable for certainapplications, a higher mirror density may be desirable for otherapplications. Therefore, it would be desirable to achieve displacementmultiplication for a microelectromechanical system in a manner thatallows for increased mirror density.

[0006] A tether or the like may be disposed within the interconnectionbetween a mirror elevator and the actuator(s). For instance, an actuatoror a plurality of actuators may be interconnected with an input to adisplacement multiplier, and the tether may interconnect the output ofthe displacement multiplier with the mirror elevator. This mirrorelevator may have a free end that moves away from and toward thesubstrate, depending upon the direction of the movement of theactuator(s). This then raises and/or tilts a mirror that may beinterconnected with the elevator.

[0007] One previously contemplated configuration for the above-notedtether was to form the same from a single layer of a structural materialin a surface micromachined optical system. This resulted in the tetherbeing flexible.

SUMMARY

[0008] Generally, the present invention is embodied in amicroelectromechanical (MEM) system having what may be characterized asa lift assembly that is elevatable from a substrate in response to aninput displacement that is typically (although not required to be) atleast generally parallel with the substrate. The substrate is one thatis appropriate for MEM applications. The lift assembly is operable tomove an end of an elevation member of the lift assembly at leastgenerally away from or toward the substrate in response to an inputdisplacement, where the movement of the elevation member's free end atleast generally away from or toward the substrate is “multiplied”without requiring the use of a separate displacement multiplier. Anyappropriate microstructure may be interconnected with this elevationmember and for any appropriate application, including without limitationa mirror microstructure for any appropriate optical application (e.g.,optical switches, attenuators, multiplexers, and de-multiplexers).

[0009] A MEM system of a first aspect of the present invention ispreferably fabricated by surface micromachining, although other MEMfabrication techniques or combination of fabrication techniques may beutilized as desired/required. In any case, the MEM system includes: asubstrate; any appropriate actuator that is movably interconnected withthe substrate in any appropriate manner; a first elevation member thatis interconnected with the substrate at a first location (e.g., at oneend of the first elevation member, although the first elevation membercould be interconnected with the substrate at an intermediate locationthat is between a pair of its ends) and a free end that is movable atleast generally away from or toward the substrate, depending upon thedirectional movement of the actuator; and a coupling or “tether” that isdisposed between and interconnects the actuator to a portion of thefirst elevation member that is able to move at least generally away fromor toward the substrate. Any configuration may be used for this tether.What is important is that the tether attaches to the first elevationmember at a location that is between the first location where the firstelevation member is interconnected with the substrate and a free endthereof. The benefit of attaching the tether to a location that isbetween where the first elevation member is interconnected with thesubstrate and a free end of the first elevation member is that, byadjusting the attachment location along the length of the firstelevation member, the displacement of the first elevation member's freeend may be altered (i.e., multiplied/amplified) with respect to theinput displacement without requiring the use of a separate displacementmultiplier. Since the MEM system of the first aspect does not requirethe use a displacement multiplier to produce a multiplied lift for thefirst elevation member (that is often necessary in various opticalapplications and possibly others as well), more room on the substrate isavailable for other microstructures. Accordingly, a higher packingdensity of microstructures (e.g., mirrors) may be achieved on thesubstrate.

[0010] Various refinements exist of the features noted in relation tothe first aspect of the present invention. Further features may also beincorporated in the first aspect of the present invention as well. Theserefinements and additional features may exist individually or in anycombination. The first elevation member in the case of the first aspectagain is interconnected with the substrate at a first location and has afree end that is operable to move at least generally away from thesubstrate in response to an input displacement. Any type of motion ofthe free end of the first elevation member may be utilized and in anymanner that is at least generally away from or toward the substrate. Inone embodiment, the free end moves along a path that is at leastgenerally within a plane that is at least generally perpendicular to thesubstrate. In another embodiment, the free end moves along a path thatis at least generally within a plane that is disposed innon-perpendicular relation to the substrate. In another embodiment themovement of the free end of the first elevation member is not confinedto being within a reference plane.

[0011] Any way of interconnecting the first elevation member with thesubstrate in a manner that allows a free end thereof to at leastgenerally move away from or toward the substrate may be utilized. Thefirst elevation member may be compliantly attached to the substrate suchthat the portion of the first elevation member between the firstlocation and its free end is able to rotate or “pivot” about thisconnection point, and thus allow this free end to move at leastgenerally away from or toward the substrate with a displacement that hasboth a component that is lateral to the substrate and a component thatis perpendicular to the substrate (e.g., along an arcuate path). In oneembodiment, a portion of the first elevation member is connecteddirectly to the substrate at the first location, and the first elevationmember “bends” or flexes to provide the desired motion for the free endof the first elevation member at least generally away from or toward thesubstrate. In this configuration, the first elevation member may havefirst and second cross-sectional areas along its length. As will beappreciated, if the entire first elevation member is made of the samematerial (e.g., polycrystalline silicon) and in the same structurallayer, the portion of the first elevation member with the smallercross-sectional area will have a smaller moment of inertia about aparticular axis and, thus, will be less stiff than the largercross-sectional area portion. Accordingly, this smaller cross-sectionalportion may be formed over that portion of the first elevation memberthat is attached to the substrate and act as what may be characterizedas an integral flexible/compliant hinge, thereby allowing the free endof the first elevation member to move at least generally away from ortoward the substrate.

[0012] In another embodiment associated with the first aspect, aseparate moving or movable hinge (e.g., multiple and discrete parts thatare movably interconnected) may be used to movably interconnect thefirst elevation member with the substrate such that the free end of thefirst elevation member is able to move at least generally away from ortoward the substrate in the desired/required manner. Any structure forestablishing this hinge and/or manner of interconnecting the hinge/hingemembers with the substrate and/or first elevation member may beutilized. In yet another embodiment of the first aspect, a compliant orflexible hinge of sorts may be used to movably interconnect the firstelevation member and the substrate. This compliant hinge may be anchoredto the substrate (e.g., by passing through one or more structural layersof a surface micromachined microelectromechanical system), and may alsobe appropriately anchored to the first elevation member. Accordingly,this compliant hinge may have a stiffness that is less than that of thefirst elevation member (and preferably a stiffness less than that of itsanchor as well) such that a force acting on the first elevation membermay bend this compliant hinge before bending the first elevation member.As will be appreciated, this compliant hinge may be formed so that ithas a first stiffness in one direction and a second stiffness in asecond direction that is greater than the first stiffness. For example,the compliant hinge may be formed as a strip with a rectangularcross-section that has a width greater than its height or thickness. Inthis embodiment, the compliant hinge will be less stiff about an axisthat is parallel with its width axis, while remaining stiffer in theaxis perpendicular to its width. In this regard, the compliant hinge maypermit the first elevation member to be pivoted in effect about only asingle axis so as to allow for controlled movement of the complianthinge and thereby the first elevation member (as well as anymicrostructure interconnected therewith).

[0013] In order to move a free end of the first elevation member atleast generally away from or toward the substrate, the MEM systemassociated with the first aspect again includes an actuator that isoperable to produce an at least generally lateral movement relativethereto (e.g., so as to move at least generally across the substrate).Any appropriate type of actuator may be utilized (e.g., electrostaticcomb actuator, a capacitive-plate electrostatic actuator, a thermalactuator, a movable-electrode electrostatic actuator, a piezoelectricactuator, an electromagnetic actuator and a magnetic actuator), and anyappropriate way of interconnecting the same with the substrate to allowrelative movement in the desired/required manner may be utilized aswell. Moreover, multiple actuators may be used and interconnected with asingle coupling or tether to exert the desired force on the firstelevation member to move a free end thereof at least generally away fromor toward the substrate. For example, a pair of actuators may be used inparallel, where the separate actuators are coupled by a laterallymoveable yoke formed on the substrate. In this regard, the tether thatinterconnects the actuators with the elevation member may beinterconnected (directly or indirectly) to this yoke so the combinedforce of the separate actuators is applied to the first elevation memberthrough the tether.

[0014] The actuator microstructure is interconnected with the firstelevation member and operable to provide the displacement that has theeffect of moving a free end of the first elevation member at leastgenerally away from or toward the substrate in the subject first aspect.In this regard, a laterally movable output of the actuatormicrostructure may be transferred to the first elevation member by acoupling or “tether” as noted above, where one end of the tether may beattached directly to the actuator microstructure and another end of thetether may be directly attached to the first elevation member betweenthe first location where the first elevation member is interconnectedwith the substrate and a free end thereof. That is, in one embodimentthere is no “intermediate” structure in the interconnection of theactuator with the connector (e.g., no displacement multiplier). When theactuator microstructure is engaged, such as to produce an “in-plane” orlateral displacement, the tether exerts a force on the first elevationmember and thereby moves a free end thereof at least generally away fromor toward the substrate. In another embodiment, an actuator may be usedin conjunction with a displacement multiplier where the first elevationmember is attached to the output of a displacement multiplier by thenoted tether and where the input of the displacement multiplier isinterconnected with the actuator.

[0015] The tether in the case of the subject first aspect is disposed orlocated at least somewhere between the actuator and the first elevationmember, and interconnects the actuator to a location that is between thefirst location where the first elevation member is interconnected withthe substrate and a free end thereof. As noted, the tether may be usedto exert a force on the first elevation member so as to move a free endthereof at least generally away from the substrate when the actuatorproduces an in-plane or lateral displacement. In addition, the tethermay be used to move the free end of the first elevation member back atleast toward the plane of the substrate when the actuator is disengagedor moved in an opposite direction than that which moved the free end atleast generally away from the substrate. Typically, themicroelectromechanical system of the first aspect will use bothdirections of motion of the first end of the first elevation member. Forinstance, a pair of first elevation members may be interconnected with amirror microstructure. Movement of the first free end of both of thesefirst elevation members at least generally away from the substrate maybe used to achieve one position for the mirror microstructure.Thereafter, the free end of one of the first elevation members may bemoved at least generally away from or toward the substrate to tilt themirror microstructure in a desired manner. Moreover, the first ends ofboth first elevation members may be moved at least generally away fromor toward the substrate to tilt the mirror microstructure in a desiredmanner or to “lower” the mirror microstructure.

[0016] Any appropriate configuration for the first elevation member maybe utilized by the first aspect of the present invention, as well as anymanner of movably interconnecting the same with the substrate. Forinstance, the first elevation member could be a single simple beam.Another option would be to define the first elevation member by aplurality of legs or beams that are appropriately interconnected. One ormore cross beams may extend between and interconnect two or more ofthese legs to provide a desired degree of rigidity to the firstelevation member.

[0017] To produce a multiplied displacement in the first elevationmember with a component that is at least generally away from or towardthe substrate in the case of the first aspect, a first end of the tethermay be interconnected with the first elevation member at a point that isbetween the first location where the same is interconnected with thesubstrate and a free end thereof, and a second end of the tether may beinterconnected with the actuator. Further, the system may be arrangedsuch that the actuator and the end of the tether interconnectedtherewith (the second end) are maintained in a fixed positionalrelationship during movement of the actuator such that the actuator andthe second end of the tether move in a one-to-one ratio. Contrast thiswith situations where a displacement multiplier interconnects theactuator with the noted second end of the tether. In this case, thesecond end of this tether (attached to the output of the displacementmultiplier) would move more than the actuator because of themultiplication provided by the displacement multiplier.

[0018] The tether associated with the first aspect may be attachedanywhere between a free end of the first elevation member and the firstlocation where the first elevation member is interconnected with thesubstrate, such that the tether transmits the displacement from theactuator to the first elevation member. Therefore, when the actuator ismoved relative to the substrate (whether actively by an appropriatesignal, passively by a spring force from one or more sources, by acombination thereof, or in any other manner), the tether may exert aforce on the first elevation member, causing the first elevation memberto pivot with respect to the substrate at least generally at/about thefirst location. As will be appreciated, this pivoting produces anangular displacement of the first elevation member and, by moving thetether attachment point on the first elevation member closer to thepivot point, a greater angular displacement of the first elevationmember can be obtained using the same input displacement. Accordingly,depending on the length of the first elevation member, the length of thetether and the displacement stroke of the actuator, a displacement of afree end of the first elevation member that is greater than the inputdisplacement of the actuator may be produced.

[0019] A second aspect of the present invention is embodied in amicroelectromechanical system that includes what may be characterized asa lever or a lever assembly that is interconnected with a substrate thatis used in the fabrication of the microelectromechanical system. Thecoupling is interconnected with the lever at a second location that isdisposed between a first free end of the lever (“free” in the sense thatit is able to move relative to the substrate) and a first location wherethe lever is interconnected with the substrate (e.g., a part of thelever that does not move laterally relative to the substrate or in adimension that is at least generally parallel with the substrate, suchas by being anchored to the substrate). This first location may define apivot point or axis of sorts. In any case, a force is exerted on thecoupling, which is then transferred to the lever at the second locationwhere the coupling interfaces with the lever. The first free end of thelever then moves relative to the substrate in response to theapplication of this force to the lever.

[0020] Various refinements exist of the features noted in relation tothe second aspect of the present invention. Further features may also beincorporated in the second aspect of the present invention as well.These refinements and additional features may exist individually or inany combination. The attachment of the coupling to the lever at thesecond location that is between its first free end and the firstlocation where the lever is interconnected with the substrate amplifiesthe amount that the first free end of the lever moves in response to acertain lateral movement of an opposite end of the coupling, incomparison to attaching the coupling directly to the first free end ofthe lever. For instance, an actuator assembly (e.g., one or moreactuator microstructures) may be interconnected with an end of thecoupling that is opposite that which interfaces with the lever at thesecond location in this second aspect. Assume that the stroke of theactuator assembly is fixed at a first distance. For this same firstdistance, a variety of different displacements of the first free end ofthe lever may be realized by changing the attachment point of thecoupling to the lever. Moving the attachment point of the coupling tothe lever so as to be closer to the first location amplifies thedisplacement of the first free end of the lever for the same fixeddisplacement of the actuator assembly.

[0021] Any configuration for the lever may be utilized in relation tothe second aspect. For instance, the lever may be defined by single beamor may be defined by a plurality beams that are structurallyinterconnected. A single coupling may be interconnected with amulti-beam lever structure so as to simultaneously move each of thevarious beams (e.g., by attaching to an interconnecting beam). Multiplecouplings could also be utilized.

[0022] Any appropriate way of establishing the above-noted “firstlocation” on the lever may be utilized in relation to the second aspect.For instance, the lever may be anchored to an underlying structure ofthe microelectromechanical system at the first location, such as thesubstrate. One way to characterize the lever is that the same is movablyinterconnected with another portion of the microelectromechanicalsystem, for instance by using a multi-piece hinge, pivot, or bearingconfiguration, or by using one or more compliant members and/orcompliant properties (e.g., to allow for a certain degree of flexure orthe like, to in turn allow for the desired movement of the first freeend of the lever relative to the substrate).

[0023] Movement of the first free end of the lever relative to thesubstrate may be in any direction and along any appropriate path. In oneembodiment, the first free end of the lever moves at least generallyaway from the substrate. This movement may be within a reference planethat is at least generally perpendicular to the substrate, within areference plane that is disposed in non-perpendicular relation to thesubstrate, or in any manner that is at least generally away from ortoward the substrate (e.g., the movement of the first free end need notbe confined to being within a reference plane). In another embodiment ofthe subject second aspect, the first free end of the lever moves withina reference plane that is at least generally parallel with thesubstrate.

[0024] The third through the sixth aspects generally relate to theidentification that the use of a flexible coupling or tether to transfermotion from an actuator assembly to a lever may adversely affect one ormore aspects of a microelectromechanical system that uses such a leverin at least certain applications (for instance, optical). Consider thecase where a lever (of any appropriate configuration, and including forexample a single beam or a plurality of appropriately interconnectedbeams) is interconnected with a substrate that is appropriate formicroelectromechanical applications, that this interconnection allowsfor movement of a first end of the lever at least generally about afirst location, where a microstructure(s) (e.g., a mirror) isinterconnected with a portion of this lever that is able to moverelative to the substrate, and where an elongate tether or couplinginterconnects (directly or indirectly) the lever with an actuatorassembly (e.g., one or more actuators that are appropriate formicroelectromechanical applications). When the actuator assembly movesrelative to the substrate, to in turn move both the tether and the firstfree end of the lever relative to the substrate, the magnitude of thetotal external forces that are experienced by the tether (e.g., anactuation force (including a resultant force) that is intended to movethe tether from one position to another; inertial forces from movementof the lever and any microstructure interconnected therewith), themanner in which these external forces are exerted on the tether (e.g.,how abruptly the actuation force is terminated), or both may be suchthat a tether of insufficient stiffness would tend to flex or bowbetween its two opposite ends. Any such elastic deformation or bucklingof the tether may adversely affect the control of the movement of themicrostructure(s) that is interconnected with the movable portion of thelever. Not only could the transmission of the actuation force to themicrostructure interconnected with the lever be somewhat delayed by anysignificant amount of flexing of the tether, but a flexed tether wouldeventually release the elastic energy stored therein to either “slap” oraccelerate the interconnected microstructure in the direction of motionor otherwise cause the interconnected microstructure to vibrate oroscillate after the motion of the actuator assembly has been terminated.The third through the sixth aspects of the present invention address theidentification of this potential problem.

[0025] A third aspect of the present invention is embodied in amicroelectromechanical (MEM) system having a lever that isinterconnected with but movable relative to a substrate in response toan input displacement that is typically, at least generally, parallelwith the substrate. The substrate is one that is appropriate for use inthe fabrication of microelectromechanical systems. A free end of thelever moves at least generally about a first location (e.g., where thelever is anchored to the substrate or otherwise movably interconnectedwith the substrate) and relative to the substrate in response to aninput displacement. Any appropriate microstructure may be interconnectedwith any portion of the lever that is movable relative to the substrateand for any appropriate application, including without limitation amirror microstructure for optical applications.

[0026] The MEM system of the third aspect of the present invention ispreferably fabricated by surface micromachining, although otherfabrication techniques or combination of fabrication techniques may beutilized as desired/required. In any case, the MEM system of the thirdaspect includes a substrate, an actuator assembly that is movablyinterconnected with the substrate in any appropriate manner, a firstlever that is interconnected with the substrate for movement at leastgenerally about a first location and that has a first free lever endthat is movable relative to the substrate at least generally about thefirst location, and an elongate coupling or “tether” that is disposedbetween and interconnects the actuator assembly and the first lever(either directly or indirectly). Any configuration may be used for thistether. What is important is that the tether is sufficiently stiff so asto withstand the external forces applied thereto without substantiallybowing or buckling.

[0027] The benefit of using a tether that is sufficiently stiff towithstand the external forces that may be applied to the tether due/inresponse to a movement of the actuator assembly (including how themotion of the actuator assembly is initiated and/or maintained, as wellas how the motion of the actuator assembly is terminated) in accordancewith the third aspect is that a slapping and/or oscillatory effectassociated with less stiff tethers is eliminated or at leastsignificantly reduced. For example, a tether that will flex or bow whenexposed to external forces of at least a certain magnitude will resultin elastic energy being stored within the tether. When this elasticenergy is released, this may cause a free end of the lever to acceleratein an undesired manner, may cause this free end of the lever to vibrateor oscillate, or both. The release of this elastic energy maysignificantly adversely affect the ability to precisely control theoperation of the microelectromechanical system, may cause undesiredcontact between components of the microelectromechanical system andpossibly resulting structural damage, or both. Using a stiff tether(such that no significant elastic energy is stored in the tether as aresult of typical external forces being exerted thereon) in accordancewith the third aspect addresses these types of deficiencies. Stifftethers also may allow for increasing the switching speed in the casewhere the third aspect is used in an optical application (e.g., when amirror microstructure is interconnected with a portion of the firstlever that is movable relative to the substrate).

[0028] Various refinements exist of the features noted in relation tothe third aspect of the present invention. Further features may also beincorporated in the third aspect of the present invention as well. Theserefinements and additional features may exist individually or in anycombination. Initially, the features discussed above in relation to thefirst and second aspects may be utilized in the subject third aspect inany combination. Any appropriate configuration may be used for the leverthat is associated with the third aspect that provides the desiredstiffness. Moreover, any way of interconnecting the lever with thesubstrate to allow its first free lever end to move relative to thesubstrate may be utilized as well. Movement of the first free lever endrelative to the substrate may be in any direction and along anyappropriate path. In one embodiment, the first free lever end moves atleast generally away from or toward the substrate, depending upon thedirection of motion of the actuator assembly. This type of movement maybe within a reference plane that is at least generally perpendicular tothe substrate, within a reference plane that is disposed innon-perpendicular relation to the substrate, or in any manner that is atleast generally away from or toward the substrate (e.g., the movement ofthe first free lever end need not be confined to being within areference plane). In another embodiment of the subject third aspect, thefirst free lever end moves within a reference plane that is at leastgenerally parallel with the substrate.

[0029] The tether in the case of the third aspect may be used to pullthe first free lever end away from the substrate when the actuatorproduces an in-plane displacement or one that is at least generallyparallel with the general lateral extent of the substrate (e.g., theactuator moves at least generally horizontally). In addition, the tethermay be used to lower the first free lever end back toward the substrate.In accordance with the third aspect of the present invention, the tetherhas a stiffness that is sufficient to withstand external forces (e.g.,an actuation force, inertial forces) that are applied to the tether dueto or as a result of an acceleration of the actuator assembly (positiveor negative), while moving the first free lever end relative to thesubstrate. “Withstand” in this context means without substantiallyflexing or bending.

[0030] The actuator assembly that is associated with the third aspectmay include one or more actuators that are appropriate formicroelectromechanical applications. The actuation force that is exertedon the tether may be active, passive, or some combination of active andpassive. For instance, an active force may be generated by transmittingan appropriate signal to the actuator assembly. A passive force, on theother hand, may involve the release of stored or potential energy. Forinstance, energy may be stored in the interconnecting structure betweenthe actuator assembly and the substrate, and the release of this energymay be characterized as being part of or contributing to the actuationforce. Energy that is stored in one or more other components of themicroelectromechanical system of the third aspect may also contribute tothe total actuation force that is exerted on the coupling (e.g., in aseparate compliant member that interconnects the two ends of the tetherto the relevant structure).

[0031] A fourth aspect of the present invention is embodied in amicroelectromechanical system that is fabricated using an appropriatesubstrate. The system includes a lever that is somehow movablyinterconnected with the substrate at a first location such that a firstfree lever end of the lever is able to move relative to the substrate atleast generally about the first location. An actuator assembly isinterconnected with the substrate for movement at least generally alonga first path. An elongate coupling interconnects the lever and thisactuator assembly. One end of the elongate coupling is interconnected(directly or indirectly) with the actuator assembly, while the oppositeend of the elongate coupling is interconnected (directly or indirectly)with a portion of the lever that is able to move relative to thesubstrate in a direction that depends upon the direction of theactuation force being exerted on the elongate coupling by/through amovement of the actuator assembly relative to the substrate. Movement ofthe first free lever end relative to the substrate in a first directionis accomplished by the actuator assembly moving relative to thesubstrate in a second direction that results in the exertion of what maybe characterized as a first actuation force on the elongate couplingthat is transferred to the lever. Movement of the first free lever endrelative to the substrate in a third direction (different from the firstdirection) is accomplished by the actuator assembly moving relative tothe substrate in a fourth direction (different from the seconddirection) that results in the exertion of what may be characterized assecond actuation force on the elongate coupling that is transferred tothe lever. The elongate coupling is configured to have a certain minimumbuckle strength between opposite ends of the elongate coupling thatdefines its length. The maximum actuation force that is exerted on theelongate coupling as a result of movement of the actuator assemblyrelative to the substrate during operation of the microelectromechanicalsystem has at least a first component that is directed along the firstpath. The noted minimum buckle strength of the elongate coupling isgreater than that the magnitude of this first component in the case ofthe fourth aspect.

[0032] Various refinements exist of the features noted in relation tothe fourth aspect of the present invention. Further features may also beincorporated in the fourth aspect of the present invention as well.These refinements and additional features may exist individually or inany combination. Initially, any of the features discussed above inrelation to the first and second aspects may be incorporated in thesubject fourth aspect as well, alone or in any combination. Although thefourth aspect may be appropriate for any number of applications, in oneembodiment a mirror or the like is interconnected with a portion of thelever that is able to move at least generally away from and toward thesubstrate (e.g., to lift and/or tilt a mirror relative to the substrateby interconnecting the mirror with a portion of the lever that is ableto move relative to the substrate).

[0033] Any appropriate configuration may be used for the lever that isassociated with the fourth aspect. Moreover, any way of interconnectingthe lever with the substrate may be utilized so as to allow the firstfree lever end to move relative to the substrate at least generallyabout the first location in the case of the fourth aspect (e.g., via oneor more compliant members, via a multi-piece pivot or hinge, via aconfiguration of that portion of the lever that is interconnected withthe substrate). Movement of the first free end of the lever relative tothe substrate may be in any direction and along any appropriate path. Inone embodiment, the first free lever end moves at least generally awayfrom or toward the substrate, depending upon the direction of motion ofthe actuator assembly. This type of movement may be within a referenceplane that is at least generally perpendicular to the substrate, withina reference plane that is disposed in non-perpendicular relation to thesubstrate, or in any manner that is at least generally away from ortoward the substrate (e.g., the movement of the first free lever endneed not be confined to being within a reference plane). In yet anotherembodiment of the subject fourth aspect, the first free lever end moveswithin a reference plane that is at least generally parallel with thesubstrate.

[0034] The actuator assembly that is associated with the fourth aspectmay include one or more actuators that are appropriate formicroelectromechanical applications. The actuation force applied to theelongate coupling may be active, passive, or some combination of activeand passive. An active actuation force may be generated by transmittingan appropriate signal to the actuator assembly. A passive actuationforce, on the other hand, may involve the release of stored energy. Forinstance, energy may be stored in the interconnecting structure betweenthe actuator assembly and the substrate, and the release of this energymay be characterized as being part of the actuation force. Moreover,energy may be stored in other portions of the microelectromechanicalsystem of the fourth aspect (e.g., a compliant member that interconnectsthe elongate coupling and the lever), and the release of this energy maybe characterized as being part of the actuation force.

[0035] In one embodiment of the fourth aspect, the elongate coupling hasa length of at least about 750 microns, and in another embodiment alength of at least about 1,300 microns (again, measured between its twoends). In another embodiment, the component of the actuation orrestoring force that is directed along the first path of movement of theactuator assembly is at least about 20 μN. One way in which the desiredbuckle strength may be realized for the elongate coupling utilized bythe fourth aspect is by forming the elongate coupling from multiple,spaced structural layers that are rigidly interconnected at a pluralityof intermediate locations between the opposite ends of the elongatecoupling.

[0036] There are a number of additional ways to characterize theelongate coupling of the fourth aspect being configured to have theabove noted buckle strength. One is that the elongate coupling is stiff.Others are that the movement, speed, acceleration, or any combinationthereof, of the first free lever end relative to the substrate is atleast substantially solely controlled by external forces that areexerted on the elongate coupling. That is, no significant portion of theforces that cause the first free lever end to move relative to thesubstrate are due to any internal forces that may exist within theelongate coupling due to being placed in compression as a result of theapplication of the actuation force thereto through movement of theactuator assembly in the relevant direction. Yet another is that astiffness of the elongate coupling is such that the elongate couplingundergoes at least substantially no elastic deformation when theactuator assembly exerts the actuation force on the elongate coupling tomove the first free lever end relative to the substrate through movementof the actuator assembly in the relevant direction.

[0037] A fifth aspect of the present invention is embodied in amicroelectromechanical system that is fabricated using an appropriatesubstrate. The system includes a lever that is somehow interconnectedwith the substrate such that a first free lever end of the lever ismovable relative to the substrate at least generally about a firstlocation. An actuator assembly is interconnected with the substrate formovement at least generally along a first path. An elongate couplinginterconnects the lever and the actuator assembly. This elongatecoupling is formed by a plurality of vertically spaced structural layersthat are rigidly interconnected at typically a plurality of spacedlocations (e.g., formed via surface micromachining). One end of theelongate coupling is interconnected (directly or indirectly) with theactuator assembly, while the opposite end of the elongate coupling isinterconnected (directly or indirectly) with a portion of the lever thatis able to move relative to the substrate in a direction that dependsupon the direction of the actuation force being exerted on the elongatecoupling by/through a movement of the actuator assembly. Movement of thefirst free lever end relative to the substrate in a first direction isaccomplished by a movement of the actuator assembly in a seconddirection that results in the exertion of what may be characterized as afirst actuation force on the elongate coupling that is transferred tothe lever. Movement of the first free lever end relative to thesubstrate in a third direction (different from the first direction) isaccomplished by a movement of the actuator assembly in a fourthdirection (different that the second direction) that results in theexertion of what may be characterized as second actuation force on theelongate coupling that is transferred to the lever.

[0038] Various refinements exist of the features noted in relation tothe fifth aspect of the present invention. Further features may also beincorporated in the fifth aspect of the present invention as well. Theserefinements and additional features may exist individually or in anycombination. Initially, any of the features discussed above in relationto the first and second aspects may be incorporated in the subject fifthaspect as well, alone or in any combination. Although the fifth aspectmay be appropriate for any number of applications, in one embodiment amirror or the like is interconnected with a portion of the lever that isable to move at least generally away from and toward the substrate(e.g., to lift and/or tilt a mirror relative to the substrate byinterconnecting the mirror with a portion of the lever that is able tomove relative to the substrate).

[0039] Any appropriate configuration may be used for the lever that isassociated with the fifth aspect. Moreover, any way of interconnectingthe lever with the substrate may be utilized so as to allow a free endthereof to move relative to the substrate at least generally about thefirst location in the case of the fifth aspect (e.g., via one or morecompliant members, via a multi-piece pivot or hinge, via a configurationof that portion of the lever that is interconnected with the substrate).Movement of the first free lever end relative to the substrate may be inany direction and along any appropriate path. In one embodiment, thefirst free lever end moves at least generally away from or toward thesubstrate, depending upon the direction of motion of the actuatorassembly. This type of movement may be within a reference plane that isat least generally perpendicular to the substrate, within a referenceplane that is disposed in non-perpendicular relation to the substrate,or in any manner that is at least generally away from or toward thesubstrate (e.g., the movement of the first free lever end need not beconfined to being within a reference plane). In another embodiment ofthe subject fifth aspect, the first free lever end moves within areference plane that is at least generally parallel with the substrate.

[0040] The actuator assembly that is associated with the fifth aspectmay include one or more actuators that are appropriate formicroelectromechanical applications. The actuation force that is appliedto the elongate coupling may be active, passive, or some combination ofactive and passive. An active actuation force may be generated bytransmitting an appropriate signal to the actuator assembly. A passiveforce, on the other hand, may involve the release of stored energy. Forinstance, energy may be stored in the interconnecting structure betweenthe actuator assembly and the substrate, and the release of this energymay be characterized as being part of the actuation force. Moreover,energy may be stored in other portions of the microelectromechanicalsystem of the fifth aspect (e.g., a compliant member that interconnectsthe elongate coupling and the lever), and the release of this energy maybe characterized as being part of the actuation force.

[0041] In one embodiment of the fifth aspect, the elongate coupling hasa length of at least about 750 microns, and in another embodiment alength of at least about 1,300 microns (again, measured between its twoends). Forming the elongate coupling of the fifth aspect from multiplestructural layers may provide a certain minimum buckle strength betweenthe opposite ends of the coupling. In this regard, the design of themicroelectromechanical system of the fifth aspect may be such thatactuator assembly of the fifth aspect exerts a maximum magnitude of theactuation force on the elongate coupling, and that has at least a firstcomponent that is directed along the first path. The noted minimumbuckle strength of the elongate coupling is preferably greater than thatthe magnitude of this first component in this particular embodiment ofthe fifth aspect. In one embodiment, the component of the actuationforce that is directed along the first path of movement of the actuatorassembly is at least about 20 μN.

[0042] There are a number of additional ways to characterize theelongate coupling of the fifth aspect being configured to have the notedbuckle strength. One is that the elongate coupling is stiff. Others arethat the movement, speed, acceleration, or any combination thereof, ofthe first free lever end relative to the substrate is at leastsubstantially solely controlled by external forces that are exerted onthe elongate coupling. That is, no significant portion of the forcesthat cause the first free lever end to move relative to the substrateare due to any internal forces that may exist within the elongatecoupling due to being placed in compression as a result of theapplication of the actuation force thereto through a movement of theactuator assembly in the relevant direction. Yet another is that astiffness of the elongate coupling is such that the elongate couplingundergoes at least substantially no elastic deformation when theactuator assembly exerts the actuation force on the elongate coupling tomove the first free lever end relative to the substrate through amovement of the actuator assembly in the relevant direction.

[0043] A sixth aspect of the present invention is directed to a methodfor operating a microelectromechanical system that is fabricated usingan appropriate substrate, and that includes an elongate coupling that isinterconnected with a lever. This method includes accelerating theelongate coupling. Accelerating the elongate coupling results in theelongate coupling being placed in compression at least at some point intime. This acceleration also moves a first lever end of the leverrelative to the substrate based on its interconnection with the elongatecoupling. The movement of the first lever end relative to the substrateis at least substantially solely controlled by external forces that areexerted on said elongate coupling. That is, no significant portion ofthe forces that cause the first lever end to move relative to thesubstrate are due to any internal forces that may exist within theelongate coupling due to being placed in compression by an accelerationof the elongate coupling.

[0044] Various refinements exist of the features noted in relation tothe sixth aspect of the present invention. Further features may also beincorporated in the sixth aspect of the present invention as well. Theserefinements and additional features may exist individually or in anycombination. The acceleration of the elongate coupling may be providedby or as a result of a movement of an actuator assembly relative to thesubstrate. One or more actuators of any appropriate type may be utilizedby such an actuator assembly. Movement of the actuator assembly may beactive (e.g., by applying an appropriate signal to the actuatorassembly), passive (e.g., via a return force that is exerted on theactuator assembly by a suspension that movably interconnects theactuator assembly with the substrate), or some combination thereof.There may be one or more other contributing sources to the accelerationof the elongate coupling as well. For instance, elastic energy may bestored in a compliant member that may be used to interconnect one orboth ends of the elongate coupling with adjacent portions of the system(e.g., with the lever; with the actuator assembly; with a displacementmultiplier that is disposed between and that interconnects the actuatorassembly and the elongate coupling).

[0045] Movement of the first lever end relative to the substrate in thecase of the sixth may be in any direction and along any appropriatepath. In one embodiment, the movement of the first lever end is at leastgenerally within a reference plane that is at least generallyperpendicular to the substrate. In another embodiment, the movement ofthe first lever end is at least generally within a reference plane thatis disposed in non-perpendicular relation to the substrate. In yetanother embodiment, the movement of the first lever end is at leastgenerally parallel with a lateral extent of the substrate. Typically thefirst lever end moves along an at least generally arcuate path relativeto the substrate, although other types of movements may be utilized.

[0046] One way in which the movement of the first lever end relative tothe substrate in the case of the sixth aspect may be accomplished byusing only external forces that are exerted on the elongate coupling, isby forming the elongate coupling to be sufficiently stiff or such thatit does not buckle to any significant degree when accelerated. In thisregard, features discussed above in relation to the fifth aspect may beutilized by the subject sixth aspect as well.

[0047] A seventh aspect of the present invention is embodied in amicroelectromechanical system that is fabricated utilizing anappropriate substrate. A lever assembly of any appropriate configurationis interconnected with this substrate such that at least part thereof isable to move both at least generally away from and toward the substrate,depending upon the direction of the force being exerted on the leverassembly. In this regard, the microelectromechanical system furtherincludes an actuator assembly that is interconnected with the substratefor movement along a first path, a coupling that is appropriatelyinterconnected (directly or indirectly) with this actuator assembly, anda connector that is attached to the lever assembly and that is alsoattached to the coupling. As such, movement of the actuator assemblyrelative to the substrate is transmitted to the lever assembly throughthe coupling and the connector.

[0048] The connector associated with the seventh aspect includes firstand second connector ends and first and second flex link assemblies. Thesecond connector end is located between the first connector end and theactuator assembly, and the coupling is attached to the connector atleast at the first connector end. Both the first and second flex linkassemblies extend between and interconnect the first and secondconnector ends. Finally, the connector includes a first interconnectthat extends between and interconnects the first flex link assembly andone portion of the lever assembly, as well as a second interconnect thatextends between and interconnects the second flex link assembly andanother portion of the lever assembly.

[0049] Various refinements exist of the features noted in relation tothe seventh aspect of the present invention. Further features may alsobe incorporated in the seventh aspect of the present invention as well.These refinements and additional features may exist individually or inany combination. The lever assembly may be characterized as an elevationstructure, which may be of any appropriate configuration. The leverassembly may be of any configuration or structure that may beinterconnected with the substrate so that at least a portion thereof isable to move at least generally away from or toward the substrate,depending upon the direction of the forces being exerted thereon. Anyappropriate device(s) may be interconnected with this elevationstructure (e.g., a mirror microstructure) and in any appropriate manner.In one embodiment, a cross beam extends between and interconnectslaterally spaced portions of the lever assembly, and the connector islocated somewhere between the location of this cross beam and thelocation where the lever assembly is movably interconnected with thesubstrate. That is, the first connector end is spaced from the crossbeam in this embodiment, which may be characterized as a free end of theelevation structure. As such, the various features discussed above inrelation to the first, second, and third aspects may be utilized by thisseventh aspect as well, alone or in any combination.

[0050] Any way of movably interconnecting the lever assembly with thesubstrate may be utilized. Surface micromachining may be used to defineat least part of the microelectromechanical system of the seventhaspect. In this case, the lever assembly may be interconnected with thesubstrate by a compliant flexure to allow a free end of the leverassembly to move at least generally away from or toward the substrate,depending upon the direction of movement of the actuator assembly. Eachcompliant flexure may be attached to a corresponding portion of thelever assembly and also attached to the substrate by an appropriateanchor.

[0051] The first and second connector ends and the first and second flexlink assemblies of the connector that are utilized by the seventh aspectmay be characterized as collectively defining a frame having a closedperimeter. This frame is at least generally rectangular in oneembodiment. Other frame configurations/profiles may be appropriate(e.g., diamond-shaped). In any case, the first interconnect couldthereby extend from one side of the connector frame to one portion ofthe lever assembly, while the second interconnect could extend from anopposite side of the connector frame to another portion of the leverassembly. Another way of characterizing the general configuration of theconnector associated with the seventh aspect is that the first andsecond flex link assemblies may be disposed at least generally parallelwith the coupling, while the first and second connector ends may bedisposed at least generally transverse to the coupling. Other relativeorientations may be appropriate.

[0052] Surface micromachining may be used to fabricate all or part ofthe microelectromechanical system of the seventh aspect of the presentinvention. In one embodiment, the connector is formed in a single levelby surface micromachining. In another embodiment, the connector and aportion of the lever assembly that is interconnected with the connectorare fabricated at a common level by surface micromachining. In yetanother embodiment, a portion of the lever assembly that isinterconnected with the connector is fabricated at one level by surfacemicromachining, while the connector is fabricated at a different level(e.g., “higher” or a level that is located further from the substrate)by surface micromachining.

[0053] There are a number of options in relation to how the couplinginterfaces with the connector in the seventh aspect. In one embodiment,the coupling is attached to both of the first and second connector ends.Another embodiment has the sole interconnection between the coupling andthe connector being at the first connector end. In this case, it may bedesirable to have a supporting beam that extends between the first andsecond connector ends.

[0054] The first and second interconnects may be exposed to a torsionalforce by the application of a pulling or pushing force on the couplingin the case of the seventh aspect. This torsional force may place atensile force on the entirety of the first and second flex linkassemblies. In one embodiment, the first and second interconnects aredisposed along a common reference axis that is at least generallytransverse to the coupling. Other relative orientations may be utilizedfor the first and second interconnects. For instance, the first andsecond interconnects each may be disposed at an angle relative to areference axis that is transverse to the coupling. Locationally, thefirst and second interconnects may each merge with the first and secondflex link assemblies, respectively, at a location that is “midway”between the first and second connector ends. However, each of the firstand second interconnects may merge with the first and second flex linkassemblies, respectively, at other locations between the first andsecond connector ends. For instance, the first and second interconnectsmay merge with the first and second flex link assemblies, respectively,at different locations between the first and second connector ends.Stated another way and considering that the coupling defines alongitudinal dimension, the first and second interconnects may belongitudinally offset relative to each other.

[0055] The actuator assembly may move in first and second directionsalong the first path in the case of the seventh aspect. Movement in thefirst direction may be utilized to move the free end of the leverassembly at least generally away from the substrate. Movement in thesecond direction may be utilized to move the noted free end(s) at leastgenerally toward the substrate. Part of the connector may be incompression and part of the connector may be in tension, regardless ofwhether the actuator assembly is moving in the first or seconddirection. Consider the case where the actuator assembly is moving inthe first direction and which places the coupling in tension. In thiscase, that portion of the first and second flex link assemblies that isbetween the first connector end and where the first and secondinterconnects merge with the first and second flex link assemblies,respectively, may be in compression, while that portion of the first andsecond flex link assemblies that is between the second connector end andwhere the first and second interconnects merge with the first and secondflex link assemblies, respectively, may be in tension. Now consider thecase where the actuator assembly is moving in the second direction andwhich places the coupling in compression. In this case, that portion ofthe first and second flex link assemblies that is between the firstconnector end and where the first and second interconnects merge withthe first and second flex link assemblies, respectively, may be intension, while that portion of the first and second flex link assembliesthat is between the second connector end and where the first and secondinterconnects merge with the first and second flex link assemblies,respectively, may be in compression.

[0056] One advantage of the configuration of the connector that isutilized by the seventh aspect is that it enhances one or more aspectsof the manner in which the motion of the coupling is transferred to thelever assembly. As discussed above in relation to the fourth, fifth, andsixth aspects, certain configurations for the coupling also may provideone or more advantages in relation to the transfer of forces to anelevation structure. Therefore, any of the features discussed above inrelation to one or more of the fourth, fifth, and sixth aspects of thepresent invention may be used alone or in any combination with thesubject seventh aspect (and vice versa).

[0057] An eighth aspect of the present invention is embodied by amicroelectromechanical system that is fabricated using an appropriatesubstrate. A lever assembly is interconnected with this substrate suchthat at least part thereof is able to move both at least generally awayfrom and toward the substrate, depending upon the direction of the forcebeing exerted on the lever assembly. In this regard, themicroelectromechanical system further includes an actuator assembly thatis interconnected with the substrate for movement along a first path, acoupling that is appropriately interconnected (directly or indirectly)with this actuator assembly, and a connector that is attached to thelever assembly, and that is also attached to the coupling. As such,movement of the actuator assembly relative to the substrate istransmitted to the lever assembly through the coupling and theconnector. Part of the connector is in compression and part of theconnector is in tension, regardless of whether the actuator assembly ismoving in the first or second direction in the case of the eighthaspect.

[0058] Various refinements exist of the features noted in relation tothe eighth aspect of the present invention. Further features may also beincorporated in the eighth aspect of the present invention as well.These refinements and additional features may exist individually or inany combination. One appropriate configuration for the connectorincludes first and second connector ends that are spaced in thedirection of the elongation or length dimension of the coupling (e.g.,longitudinally spaced). The second connector end is located between thefirst connector end and the actuator assembly, and the coupling isattached at least to at least the first connector end (e.g., thecoupling may also be attached to the second connector end). Theconnector may also include first and second flex link assemblies thatextend between the first and second connector ends on opposite sides ofthe coupling, and first and second interconnects that extend from thefirst and second flex link assemblies, respectively, to differentportions of the lever assembly. Movement of the actuator assembly in thefirst direction may move part of the lever assembly (e.g., a free end(s)of the lever assembly) at least generally away from the substrate andmay place the coupling in tension. In this case, that portion of thefirst and second flex link assemblies that is between the firstconnector end and where the first and second interconnects merge withthe first and second flex link assemblies, respectively, may be incompression, while that portion of the first and second flex linkassemblies that is between the second connector end and where the firstand second interconnects merge with the first and second flex linkassemblies, respectively, may be in tension. Movement of the actuatorassembly in the second direction may move part of the lever assembly atleast generally toward the substrate (e.g., a free end(s) of the leverassembly) and may place the coupling in compression. In this case, thatportion of the first and second flex link assemblies that is between thefirst connector end and where the first and second interconnects mergewith the first and second flex link assemblies, respectively, may be intension, while that portion of the first and second flex link assembliesthat is between the second connector end and where the first and secondinterconnects merge with the first and second flex link assemblies,respectively, may be in compression. Each of features that werediscussed above as being relevant to the seventh aspect also may beutilized by this eighth aspect as well, alone and in any combination.

[0059] A ninth aspect of the present invention is embodied in amicroelectromechanical system that is fabricated using an appropriatesubstrate. A lever assembly is interconnected with this substrate suchthat at least part thereof is able to move both at least generally awayfrom and toward the substrate, depending upon the direction of the forcebeing exerted on the lever assembly. In this regard, themicroelectromechanical system further includes an actuator assembly thatis interconnected with the substrate for movement along a first path, atether or coupling that is appropriately interconnected (directly orindirectly) with this actuator assembly, and a connector that isattached to both the lever assembly and the coupling. As such, movementof the actuator assembly relative to the substrate is transmitted to thelever assembly through the coupling and the connector.

[0060] Various refinements exist of the features noted in relation tothe ninth aspect of the present invention. Further features may also beincorporated in the ninth aspect of the present invention as well. Theserefinements and additional features may exist individually or in anycombination. In one embodiment, the connector of the eighth aspectincludes at least one flex link or a structure that will flex more thanthe lever assembly when exposed to the types of forces exerted on theconnector during normal operation. In another embodiment, at least oneflex link of the connector is placed in compression and at least oneflex link of the connector is placed in tension, regardless of whetherthe coupling is being placed in tension or compression by a movement ofthe actuator assembly. Stated another way, at least one flex link of theconnector is placed in compression and at least one flex link of theconnector is placed in tension, regardless of which direction theactuator assembly is moving relative to the substrate. In yet anotherembodiment, at least one flex link of the connector on each side of thecoupling is placed in compression and at least one flex link of theconnector on each side of the coupling is placed in tension, regardlessof which direction the actuator assembly is moving relative to thesubstrate.

DESCRIPTION OF THE DRAWINGS

[0061]FIG. 1 shows a schematic plan view of one embodiment of an opticalsystem with a pair of lift assemblies that are configured fordisplacement multiplication;

[0062]FIG. 2 shows a side view of one of the lift assemblies of FIG. 1,in an elevated position away from the plane of the substrate;

[0063]FIG. 3A is an enlarged plan view of one of the lift assemblies ofFIG. 1.

[0064]FIG. 3B is an enlarged plan view of a variation of the liftassembly of FIG. 3A that provides yet further multiplied displacement inrelation to the FIG. 3A embodiment;

[0065]FIG. 3C is a plan view of another variation of the lift assemblyof FIG. 3A;

[0066]FIG. 3D is a plan view of another variation of the lift assemblyof FIG. 3A;

[0067]FIG. 3E is a plan view of another variation of the lift assemblyof FIG. 3A;

[0068]FIGS. 4A and 4B show a schematic side view of the operation of thelift assemblies of FIGS. 3A and 3B respectively;

[0069]FIG. 5 shows a schematic plan view of another embodiment of anoptical system with a lift assembly that is configured for displacementmultiplication;

[0070]FIG. 6A is a side view of a microelectromechanical system with oneembodiment of a displacement multiplication system;

[0071]FIG. 6B is a top view of the system of FIG. 6A;

[0072]FIG. 6C is an end view of a plane of motion of a lever of themicroelectromechanical system of FIG. 6A;

[0073]FIG. 6D is a variation of the displacement multiplication systemof the microelectromechanical system of FIG. 6A;

[0074]FIG. 6E is an end view of a plane of motion of a lever of themicroelectromechanical system of FIG. 6A;

[0075]FIG. 7 is a top view of a microelectromechanical system withanother embodiment of a displacement multiplication system;

[0076]FIG. 8 is a side view of one embodiment of a multi-layered tetherto provide a desired stiffness;

[0077]FIG. 9 is a perspective view of one embodiment of a positioningsystem with one embodiment of a connector between a coupling/tether andan elevation structure;

[0078]FIG. 10 is a perspective view of a variation of the positioningsystem of FIG. 9 in relation to the connector between thecoupling/tether and the elevation structure;

[0079]FIG. 11 is a perspective view of a variation of the positioningsystem of FIG. 9 in relation to the connector between thecoupling/tether and the elevation structure;

[0080]FIG. 12 is a perspective view of a variation of the positioningsystem of FIG. 9 in relation to the connector and the coupling/tether;

[0081]FIG. 13 is a perspective view of a variation of the positioningsystem of FIG. 9 in relation to the connector and the coupling/tether;and

[0082]FIG. 14 is a perspective view of a variation of the positioningsystem of FIG. 9 in relation to the connector between thecoupling/tether and the elevation structure.

DETAILED DESCRIPTION

[0083] The present invention will now be described in relation to theaccompanying drawings which at least assist in illustrating its variouspertinent features. Surface micromachined microstructures are thegeneral focus of the present invention. Various surface micromachinedmicrostructures are disclosed in U.S. Pat. No. 5,867,302, issued Feb. 2,1999, and entitled “BISTABLE MICROELECTROMECHANICAL ACTUATOR”; and U.S.Pat. No. 6,082,208, issued Jul. 4, 2000, and entitled “METHOD FORFABRICATING FIVE-LEVEL MICROELECTROMECHANICAL STRUCTURES ANDMICROELECTROMECHANICAL TRANSMISSION FORMED”, the entire disclosures ofwhich are incorporated by reference in their entirety herein.

[0084] Surface micromachining generally entails depositing alternatelayers of structural material and sacrificial material using anappropriate substrate which functions as the foundation for theresulting microstructure, which may include one or more individualmicrostructures. The term “substrate” as used herein means those typesof structures that can be handled by the types of equipment andprocesses that are used to fabricate micro-devices on, within, and/orfrom the substrate using one or more micro photolithographic patterns.An exemplary material for the substrate is silicon. Various patterningoperations (collectively encompassing the steps of masking, etching, andmask removal operations) may be executed on one or more of these layersbefore the next layer is deposited so as to define the desiredmicrostructure. After the microstructure has been defined in thisgeneral manner, at least some of the various sacrificial layers areremoved by exposing the microstructure and the various sacrificiallayers to one or more etchants. This is commonly called “releasing” themicrostructure from the substrate, typically to allow at least somedegree of relative movement between the microstructure and thesubstrate. The term “sacrificial layer”, therefore, means any layer orportion thereof of any surface micromachined microstructure that is usedto fabricate the microstructure, but which does not exist in the finalconfiguration. Exemplary materials for the sacrificial layers describedherein include undoped silicon dioxide or silicon oxide, and dopedsilicon dioxide or silicon oxide (“doped” indicating that additionalelemental materials are added to the film during or after deposition).Exemplary materials for the structural layers of the microstructureinclude doped or undoped polysilicon and doped or undoped silicon. Thevarious layers described herein may be formed/deposited by techniquessuch as chemical vapor deposition (CVD) and including low-pressure CVD(LPCVD), atmospheric-pressure CVD (APCVD), and plasma-enhanced CVD(PECVD), thermal oxidation processes, and physical vapor deposition(PVD) and including evaporative PVD and sputtering PVD, as examples.

[0085] Only those portions of a microelectromechanical system that arerelevant to the present invention will be described herein. There may,and typically will, be other microstructures that are included in agiven microelectromechanical system. As used herein, the term“compliant” or “flexible” is defined to mean a first portion of amicrostructure that is less stiff in comparison with an attached secondportion of that microstructure, such that the compliant or flexiblefirst portion of the microstructure will bend or flex significantly morethan the ‘stiffer’ second portion upon application of a force.

[0086] Referring now to FIG. 1, there is shown a top view of anexemplary MEM optical system 10 that is fabricated on a substrate 100.Although only one optical system 10 is shown, it will be appreciatedthat a particular chip may contain multiple sets of these MEM opticalsystems 10, along with other relevant componentry. As shown, theexemplary system 10 includes a reflective microstructure 12 (e.g.,mirror) and two sets of positioning microstructures 18, 19 which eachinclude an electrostatic actuator 30, a lift assembly or an A-framestructure 20, and a coupling or tether 40. In addition, a passive member28 attaches a peripheral edge of the reflective microstructure 12 to thesubstrate 100 such that the reflective microstructure 12 may pivot aboutthis location as well. In operation, the positioning microstructures 18,19 may be used independently or in concert to lift and/or tilt thereflective microstructure 12 relative to the substrate 100 for thedesired optical application. Any way of interconnecting the mirrormicrostructure 12 with one or more positioning microstructures 18, 19and/or the substrate 100 may be utilized to achieve a desiredresponse/movement of the mirror microstructure 12 relative to thesubstrate 100.

[0087] Each actuator microstructure 30 includes several stationary combs32 that are fixed to the substrate 100 and several moveable combs 34that are attached to a moveable frame 36. The moveable frame 36 issupported above the substrate 100 by a folded actuator support spring 56that is anchored to the substrate 100 at four anchor points 58 to permitlateral movement of the frame 36 relative to the substrate 100.“Lateral” or the like herein means at least generally parallel withrespect to the substrate 100 or a plane that at least generally containsthe substrate 100. Upon application of a control voltage via electricalinterconnects (not shown) across the combs 32, 34, the moveable combs 34are pulled laterally towards the stationary combs 32, thereby moving theframe 36 laterally relative to the substrate 100. The amount of lateralmovement corresponds with the magnitude of the actuation voltageapplied. As the movable frame 36 moves laterally, the actuator supportsprings 56 are moved from their static condition and store a returnpotential energy equal to their spring constant times this lateraldisplacement. Once the application of the control voltage is removedfrom the actuator combs 32 and 34, the actuator support springs 56return the frame 36 back to its static position. Any type of actuatormicrostructure may be utilized in place of the actuator 30(electrostatic comb actuator, a capacitive-plate electrostatic actuator,a thermal actuator, a movable-electrode electrostatic actuator, apiezoelectric actuator, an electromagnetic actuator and a magneticactuator), and any manner of movably interconnecting the same with thesubstrate 100 may be utilized as well in relation to any positioningmicrostructure 18, 19 that may be used by the optical system 10.Moreover, it should be appreciated that movement of the actuator 30 ineither direction may be accomplished in any appropriate manner. Forinstance, movement of the actuator 30 in a given direction may be via anactive force in the sense that it is in response to an appropriatesignal, may be via a passive force in the sense that it utilizes astored spring force or the like, or a combination thereof.

[0088] The frame 36 is coupled to a coupling microstructure, connectormember, or “tether” 40 which in turn is connected to the A-framestructure 20. A first end 41 of the tether 40 couples with a crossbeam26 on the A-frame structure 20 that connects the individual legs orelevation members 22 of the A-frame structure 20. Though shown near theapex or free end 24 of the A-frame structure 20, the crossbeam 26 is infact spaced from this apex 24. Generally, the crossbeam 26 may bedisposed at any location that is somewhere between the apex 24 and base70 of the A-frame structure 20, as will be more fully discussed below.The A-frame structure 20 is compliantly anchored at its base 70 to thesubstrate 100 and is connected to the reflective microstructure 12 by anextension arm 14. Where tether 40 attaches to the A-frame structure 20in this general manner provides what may be characterized as adisplacement multiplication system.

[0089] Any way of interconnecting the A-frame structure 20 and themirror microstructure 12 may be utilized by the positioningmicrostructures 18, 19. Moreover, any appropriate configuration of amicrostructure that may be moved at least generally away from or towardthe substrate 100 may be used by either of the positioningmicrostructures 18, 19, as well as any appropriate manner of movablyinterconnecting such a microstructure with the substrate 100 (e.g., thetether 40 could be attached to a single beam that is anchored to thesubstrate 100 at one location, and that has an end that is spaced fromthis location and that is movable away from the substrate 100).

[0090] Referring to FIG. 2, there is shown a side view of an A-framestructure 20 being moved away from the substrate 100 by a displacementof the tether 40 that is in turn provided by a lateral movement of thecorresponding actuator microstructure 30. As shown in FIG. 2, only oneelevation member 22 is visible. Because the A-frame structure 20 iscompliantly anchored to the substrate 100 at its base 70, when theactuator microstructure 30 moves laterally relative to the substrate 100in one direction, the apex 24 of the A-frame structure 20 moves relativeto and at least generally away from the substrate 100 along an at leastgenerally arcuate path to apply a force to the mirror microstructure 12(not shown in FIG. 2), to in turn move the reflective microstructure 12at least generally away from the substrate 100 as well (e.g., at leastwhere it is attached to the A-frame structure 20). It should beappreciated that a movement of the actuator microstructure 30 in theopposite direction will then move the apex 24 of the A-frame structure20 at least generally toward the substrate 100. In essence, the A-framestructure 20 acts as a lever arm. The longer the lever arm comprised byelevation members 22 of the A-frame structure 20, the greater the amountof upward displacement of the mirror microstructure 12 for a givenupward angular displacement of the elevation members 22.

[0091] One end of each elevation member 22 is connected to the substrate100 with what may be characterized as a hinge member 75, which containsan anchor point or post 74 and a flexible member 72. This anchor point74 may pass through one or more layers of structural material to providea secure attachment to the substrate 100. The flexible member 72attaches each elevation member 22 to its anchor point 74 and thus allowsthe A-frame structure 20 to be moved out of the plane of the substrate100. In order for the bending which results from moving the A-framestructure 20 away from the substrate 100 to be substantially isolated tothe flexible members 72, the flexible members 72 may have a lowerresistance to bending (i.e., moment of inertia) than the structures theyconnect. The moment of inertia for a structure with a rectangular crosssection is I=bh³/12, where “h” is the height of the rectangleperpendicular to the bending axis and “b” is the width of the rectangleparallel with the bending axis. Therefore, a structure's stiffness is acubic function of the height or thickness of that structure in thedirection perpendicular to the bending axis. Therefore, one way tosubstantially isolate bending to the flexible members 72 is to form theflexible members 72 such that their thickness perpendicular to thedesired bending axis is significantly less than corresponding thicknessabout the same axis of the structures they connect (e.g., the anchorpoints 74 and elevation members 22).

[0092] The crossbeam 26, which connects the elevation members 22 at apoint between the A-frame's apex 24 and base 70, allows lateraldisplacements from the actuator 30 (or any other appropriate motivesource) to act upon both elevation members 22 simultaneously.Additionally, the crossbeam 26 allows for attaching the first end 41 ofthe tether 40 to both elevation members 22 at a point other than theA-frame structure's apex 24 such that a range of multiplieddisplacements of the apex 24 away from the substrate 100 may be realizedin response to a lateral movement of the actuator microstructure 30. Asnoted above, A-frame structure 20 is, in effect, a lever arm in which agreater amount of vertical displacement with respect to the substrate100 will be produced at points further from the pivot point (i.e., theA-frame's base 70) for a given angular displacement of the A-framestructure 20. Accordingly, by attaching the first end 41 of the tether40 closer to the base 70 of the A-frame structure 20, a small lateralmovement of the tether 40 will result in a larger angular displacementof the A-frame structure 20 and its apex 24 relative to the substrate100.

[0093]FIG. 3A is an enlarged plan view of the positioning microstructure19 of FIG. 1, while FIG. 3B is an enlarged plan view of a variation ofthis positioning microstructure 19. Corresponding components aresimilarly identified in FIGS. 3A and 3B, but a “single prime”designation is utilized in FIG. 3B as being indicative of the existenceof at least one structural difference from the embodiment of FIG. 3A.Generally, the horizontal beam 26 in FIG. 3A connects the A-frameelevation members 22 at a location that is spaced from the apex 24 ofthe A-frame structure 20 by a first longitudinal distance. Thehorizontal beam 26′ in FIG. 3B connects the A-frame elevation members 22at a location that is spaced from the apex 24 of the A-frame structure20 at second longitudinal distance that is greater than the above-notedfirst longitudinal distance. That is, the crossbeam 26′ in theembodiment of FIG. 3B is positioned closer to the base 70 than thecrossbeam 26 in the embodiment of FIG. 3A. Therefore, the same magnitudeof lateral movement of the actuator microstructure 30 will produce agreater vertical displacement in the case of the embodiment of FIG. 3Bthan in the embodiment of FIG. 3A. This is depicted by a comparison ofFIGS. 4A and 4B.

[0094] Various other configurations of positioning microstructures maybe appropriate. FIG. 3C illustrates an elevation structure 476. Theelevation structure 476 includes a pair of lower legs or levers 478 a,478 b that are symmetrically disposed relative to a tether 490. One end496 a, 496 b of these lower legs 478 a, 478 b is movably interconnectedwith a substrate 498 in the same manner as the legs 22 of the A-framestructure 20. The lower legs 478 a, 478 b are joined at an intersection480, which is at an intermediate location between the ends 496 a, 496 bof the lower legs 478 a, 478 b (which collectively define one end of theelevation structure 476) and a free end 494 of the elevation structure476. A crossbeam 484 extends between and interconnects the lower legs478 a, 478 a between the ends 496 a, 496 b and the intersection 480. Asingle upper leg 482 extends from this intersection 480 to the free end494 of the elevation structure 476. A pair of appropriate and spacedinterconnects 486 extend from the upper leg 482 to a reflectivemicrostructure 488. Movement of the elevation structure 476, and therebymovement of the reflective microstructure 488, is accomplished bytransmitting an appropriate actuation force to the elevation structure476 through a tether 490. One end 492 of the tether 490 is attached tothe crossbeam 484 of the elevation structure 476, while its opposite end(not shown) is attached (directly or indirectly) with an appropriateactuator assembly (i.e., one or more actuators that are appropriate fora microelectromechanical application). As such, the actuation force isexerted on the elevation structure 476 by the tether 490 at a locationthat is spaced from its free end 494.

[0095]FIG. 3D illustrates a variation of the elevation structure 476 ofFIG. 3C. Therefore, the same reference numerals are used to identify thecorresponding structures, along with a “single prime” designation. Theelevation structure 476′ includes a pair of lower legs or levers 478 a′,478 b′ that are symmetrically disposed relative to the tether 490. Oneend 496 a′, 496 b′ of these lower legs 478 a′, 478 b′ is movablyinterconnected with the substrate 498 in the same manner as the legs 22of the A-frame structure 20. The lower legs 478 a′, 478 b′ are joined atan intersection 480′, which is at an intermediate location between theends 496 a′, 496 b′ of the lower legs 478 a′, 478 b′ (which collectivelydefine one end of the elevation structure 476′) and a free end 494′ ofthe elevation structure 476′. A single upper leg 482′ extends from thisintersection 480′ to the free end 494′ of the elevation structure 476′.A pair of appropriate and spaced interconnects 486′ extend from theupper leg 482′ to the reflective microstructure 488. Movement of theelevation structure 476′, and thereby movement of the reflectivemicrostructure 488, is accomplished by transmitting an appropriateactuation force to the elevation structure 476′ through the tether 490.One end 492 of the tether 490 is attached to the upper leg 482′ (i.e.,at any location between the free end 494′ and the intersection 480′ ofthe elevation structure 476), while its opposite end (not shown) isattached (directly or indirectly) with an appropriate actuator assembly(i.e., one or more actuators that are appropriate for amicroelectromechanical application). As such, the actuation force isexerted on the elevation structure 476′ by the tether 490 at a locationthat is spaced from its free end 494′.

[0096]FIG. 3E illustrates another variation of the elevation structure476 of FIG. 3C. Therefore, the same reference numerals are used toidentify the corresponding structures, along with a “double prime”designation. The elevation structure 476″ includes a pair of lower legsor levers 478 a″, 478 b″ that are disposed in asymmetrical relation to atether 490. One end 496 a″, 496 b″ of these lower legs 478 a″, 478 b″ ismovably interconnected with a substrate 498 in the same manner as thelegs 22 of the A-frame structure 20. The lower legs 478 a″, 478 b″ arejoined at an intersection 480″, which is at an intermediate locationbetween the ends 496 a″, 496 b″ of the lower legs 478 a″, 478 b″ (whichcollectively define one end of the elevation structure 476″) and a freeend 494″ of the elevation structure 476″. A crossbeam 484″ extendsbetween and interconnects the lower legs 478 a″, 478 a″ between the ends496 a″, 496 b″ and the intersection 480″. A single upper leg 482″extends from this intersection 480″ to the free end 494″ of theelevation structure 476″. This upper leg 482″ includes a first portionthat extends linearly from the intersection 480″ in parallel relation tothe tether 490 (and in axial alignment with the leg 478 b″), and asecond portion that extends in linear fashion at least generally in thedirection of the reflective microstructrure 488 (i.e., the first andsecond portions of the upper leg 482″ are disposed at an angle to eachother). A pair of appropriate and spaced interconnects 486″ extend fromthe upper leg 482″ to a reflective microstructure 488. Movement of theelevation structure 476″, and thereby movement of the reflectivemicrostructure 488, is accomplished by transmitting an appropriateactuation force to the elevation structure 476″ through the tether 490.One end 492 of the tether 490 is attached to the crossbeam 484″ of theelevation structure 476″, while its opposite end (not shown) is attached(directly or indirectly) with an appropriate actuator assembly (i.e.,one or more actuators that are appropriate for a microelectromechanicalapplication). As such, the actuation force is exerted on the elevationstructure 476″ by the tether 490 at a location that is spaced from itsfree end 494″.

[0097]FIGS. 4A and 4B show a side view of the operation of thepositioning microstructures 19, 19′ of FIGS. 3A and 3B, respectively(not to scale). As shown in FIG. 4A, when the first end 41 of the tether40 is connected to the A-frame structure 20 a relatively short distancefrom the apex 24, the second end 42 of the tether 40 (attached to amotive source such as the actuator microstructure 30 on the substrate100) must be moved approximately 35 microns to the left to produce thevertical displacement of apex 24 shown in FIG. 4A. In contrast, when thefirst end 41 of the tether 40′ is connected nearer the base 70 of theA-frame structure 20′ (see FIGS. 3B and 4B), this same verticaldisplacement of the apex 24 may be achieved by moving the second end 42of the tether 40′ only 5 microns to the left. By selecting theappropriate geometries between the microstructures and selectivelyattaching the first end 41 of the tether 40 to the A-frame structure 20at a certain location that is between the apex 24 and the base 70, thelateral displacement provided by an actuator 30 can produce a range ofdisplacements of a lever arm type lift system to elevate amicrostructure to a desired height above a substrate 100 without the useof a displacement multiplier.

[0098] Referring to FIG. 5, there is shown a schematic plan view ofanother embodiment of a positioning microstructure. The positioningmicrostructure 200 of FIG. 5 is configured similarly to the systems inFIGS. 3A and 3B. However, the positioning microstructure 200 shown inFIG. 5 includes a displacement multiplier 80 that is disposed betweenthe actuator 30 and the tether 40. Any configuration may be utilized forthe displacement multiplier 80. In this configuration, an input end 82of the displacement multiplier 80 is connected to the movable frame 36of the actuator microstructure 30, while an output end 84 of thedisplacement multiplier 80 is connected to the second end 42 of thetether 40. The displacement multiplier 80 is interconnected with thesubstrate 100 by a plurality of appropriately positioned anchors 88.Generally, the displacement multiplier 80 may be configured such that afirst magnitude of lateral movement of the input end 82 will produce asecond magnitude of lateral movement of the output end 84 that isdifferent from the first magnitude by a predetermined pivoting of thevarious beam microstructures that define the displacement multiplier 80.However, the displacement multiplier 80 may provide one-for-one movementbetween the input section 82 and the output section 84 as well.

[0099] The general principles of the above-described optical system inrelation to the manner of lifting and/or pivoting the mirrormicrostructure described therein are embodied by themicroelectromechanical system 300 of FIGS. 6A-C. Themicroelectromechanical system 300 is fabricated using an appropriatesubstrate 304. One component of the microelectromechanical system 300 isan actuator assembly 308 that is interconnected with the substrate 304for movement relative thereto in any appropriate manner, such as by oneor more compliant interconnects 312 or the like. The actuator assembly308 utilizes one or more actuators of any appropriate type.

[0100] Another component of the microelectromechanical system 300 is alever 316. This lever 316 may be in any appropriate configuration (e.g.,defined by a single beam; defined by a plurality of interconnectedbeams), and includes a free end 320 that is movable both at leastgenerally away from and at least generally toward the substrate 304 in amanner that is at least generally about a location 324. This location324 corresponds with an end of the lever 316 that is opposite the freeend 320 of the lever 316 in the illustrated embodiment, although suchneed not be the case (e.g., the location 324 could be at someintermediate location between the opposing ends of the lever 316). Thelocation 324 will typically coincide with where an anchor 328 extendsbetween and interconnects the lever 316 with an underlying structure,such as the substrate 304. In any case, the actuator assembly 308 isinterconnected with the lever 316 at a location 322 on the lever 316 bya coupling or tether 332. Any appropriate structure may be utilized bythe coupling or tether 332, including a single beam of sorts or aplurality of beams. Moreover, a displacement multiplier or the like maybe utilized (e.g., similar to the FIG. 5 embodiment).

[0101] Generally, the coupling 332 attaches to the lever 316 at thelocation 322, which may be disposed or located anywhere between thelocation of the free end 320 of the lever 316 and the location 324 aboutwhich the free end 320 of the lever 316 at least generally movesrelative to the substrate 304. Since the resultant vector F₁ of theforces that are exerted on the coupling 332 by a movement of theactuator assembly 308 relative to the substrate 304 is at leastgenerally collinear with the longitudinal extent of the lever 316, thefree end 320 of the lever 316 moves along an at least generally arcuatepath and within a reference plane 334 that is at least generallyperpendicular to the substrate 304. This is the type of motion utilizedby the above-described embodiments. Different types of motion may berealized, and such may be used by the above-described embodiments aswell.

[0102] One embodiment where the motion of the free end 320 of the lever316 is not within a reference plane 334 that is at least generallyperpendicular to the substrate 304 is illustrated in FIGS. 6D-E.Corresponding components of the embodiments of FIGS. 6A-C and 6D-E aresimilarly identified, although a single prime designation is used inFIGS. 6D-E to indicate that there is at least one difference betweenthese two embodiments. Generally, the primary distinction between thetwo embodiments is that the microelectromechanical system 300′ of FIGS.6D-E disposes the actuator assembly 308 in a position relative to thelever 316 such that the resultant vector F₂ of the forces that areexerted on the coupling 332 by a movement of the actuator assembly 308relative to the substrate 304 are not collinear with the longitudinalextent of the lever 316. As such, although the free end 320 of the lever316 still moves along an at least generally arcuate path relative to thesubstrate (both at least generally away from and toward the substrate304, depending upon the direction of the motion of the actuator assembly308), it does so within a reference plane 334′ that is disposed at anangle relative to the substrate 304 that is anything other thanperpendicular to the substrate 304. Other configurations/arrangementsmay allow the free end 320 of the lever 316 to move both away from andtoward the substrate 304 other than within a plane that is perpendicularto the substrate 304, and such may be utilized by themicroelectromechanical system 300′ of FIGS. 6D-E.

[0103] Another embodiment of a microelectromechanical system thatproduces a movement within yet a different reference plane isillustrated in FIG. 7. The microelectromechanical system 336 of FIG. 7is fabricated using an appropriate substrate 340. One component of themicroelectromechanical system 336 is an actuator assembly 344 that isinterconnected with the substrate 340 for movement relative thereto inany appropriate manner and by any appropriate technique. The actuatorassembly 344 may a utilize one or more actuators of any appropriatetype.

[0104] Another component of the microelectromechanical system 336 is alever 348. This lever 348 may be in any appropriate configuration (e.g.,defined by a single beam; defined by a plurality of interconnectedbeams), and includes a free end 352 that is movable relative to thesubstrate 304 at least generally about a location 360. This location 360corresponds with an end of the lever 348 that is opposite the free end352 in the illustrated embodiment, although such need not be the case(e.g., the location 360 could be at some intermediate location betweenthe opposing ends of the lever 348). The location 360 will typicallycorrespond with where the lever 360 in structurally interconnected withan underlying structure, such as the substrate 340 (e.g., correspondingwith an anchor or pin to the substrate 340).

[0105] The actuator assembly 344 is interconnected with the lever 348 ata location 356 on the lever 316 by a coupling or tether 364. Anyappropriate structure may be utilized by the coupling or tether 364,including a single beam of sorts or a plurality of beams and adisplacement multiplier or the like (e.g., similar to the FIG. 5embodiment). Generally, the coupling 364 attaches to the lever 348 atthe location 356, which may be disposed or located anywhere between thelocation of the free end 352 of the lever 348 and the location 360 aboutwhich the free end 352 of the lever 348 at least generally movesrelative to the substrate 304. The microelectromechanical system 336 isconfigured such that the free end 352 of the lever 348 moves within areference plane that is at least generally parallel with that of thesubstrate 304 (e.g., in at least generally horizontal relation). Otherconfigurations that allow the free end 352 to move in this generalmanner may be used by the microelectromechanical system 336.

[0106] Each of the above-noted tethers or couplings are subjected toexternal forces from a number of sources during operation of themicroelectromechanical system. There is of course the actuation forcethat is generated and transmitted to the tether to move the tether in acertain manner. This actuation force may be a cumulative force of theforce exerted on the tether by a movement of the actuator/actuatorassembly, as well as a spring force from one or more sources of themicroelectromechanical system. The actuation force will at least at somepoint in time expose the tether to a tensile force when the actuator oractuator assembly interconnected therewith moves in one direction, andat least at some point in time expose the tether to a compressive forcewhen this actuator/actuator assembly moves in the opposite direction(whether actively via receipt of an actuation signal by theactuator/actuator assembly, passively via a stored spring force or thelike, or a combination thereof). Inertial forces (e.g., from the mass ofthe lever and the microstructure that moves in response to the movementof the lever) will also be generated and transmitted to the tether, forinstance in response to the manner in which the motion of theactuator/actuator assembly is initiated/maintained and in the manner inwhich the motion of the actuator/actuator assembly is terminated. In atleast certain applications (e.g., to achieve a desired switching speedfor an optical application; to have a more controlled response of a loadthat is interconnected with a lever that is moved via a movement of thetether or coupling), it may be desirable to configure such a tether orcoupling to have a stiffness such that there is not any significantflexing or buckling of the tether or coupling when exposed to at least acertain magnitude of external forces. This level of stiffness may berequired, even when such tethers or couplings are incorporated into amicroelectromechanical system so as to have a length in excess of about1,300 microns, where the “x component” of the compressive external forcethat is exerted on the tether or coupling microstructure by a movementof an actuator/actuator assembly relative to the substrate is in excessof about 20 μN, or both. The “x component” means along an axis that isat least generally parallel with the general lateral extent of thesubstrate.

[0107] One way to characterize the above-noted type of stiffness is thatsuch a tether or coupling has a buckle strength between its oppositeends that is greater than a maximum “x component” of the force that willtypically be exerted on the tether or coupling by a movement of theactuator assembly so as to place the tether or coupling in compressionduring operation of the corresponding microelectromechanical system.Another way to characterize such a stiffness is that the movement,speed, acceleration, or any combination thereof, of a free end of thelever (or elevator structure) relative to the substrate is at leastsubstantially solely controlled by external forces that are exerted onthe tether or coupling. That is, for this characterization, nosignificant portion of the forces that cause a free end of the lever tomove relative to the substrate, at a time when the tether or coupling isunder compression, are due to any internal forces that may exist withinthe tether or coupling. Yet another way to characterize this type ofstiffness for the tether or coupling is that the tether or couplingundergoes at least substantially no elastic deformation when placed incompression by exposure to external forces from any source orcombination of sources. Although this “stiff” tether feature will now bedescribed in more detail in relation to the embodiment of FIGS. 1-2,these fundamentals are equally applicable to any of the embodimentsdescribed herein if desired/required by a particular application.

[0108] Referring back now to the embodiment of FIGS. 1 and 2, the tether40 again interconnects the actuator's movable frame 36 to the beam 26interconnecting the elevation members 22 of the A-frame structure 20.This tether 40 is used to transfer the displacement from the actuator 30to the A-frame structure 20, which, in turn, produces the angulardisplacement of the A-frame structure 20 that moves the reflectivemicrostructure 12 relative to the substrate 100. As will be appreciated,the actuation force that is applied by the movable frame 36 of theactuator 30 to the second end 42 of the tether 40 for lifting thereflective microstructure 12 away from the substrate 100 is a pullingforce, which is represented as a tensile force in the tether 40.However, upon reduction of the electrical voltage across the actuatorcombs 32 and 34, the actuator support springs 56 connected between themovable frame 36 and the substrate 100 apply a pushing or compressiveforce to the tether 40 since the opposite end 41 of the tether 40 isstructurally interconnected with the reflective microstructure 12. Thisis also an actuation force. Other spring forces may be exerted on thetether 40 as well and contribute to the actuation force that is exertedon the tether 40. For instance, the compliant member 43 between thetether 40 and the movable frame 36 of the actuator 30, the compliantmember 43 between the tether 40 and the A-frame structure 20, and/or theflexible member 72 between the elevation members 22 and the substrate100 may apply a spring force to the tether 40 that is directed to movethe tether 40 relative to the substrate 100. It should be appreciatedthat an actuation force that moves the apex of the A-frame structure 20toward the substrate 100 could of course be applied to the tether 40 byan actuated movement of the actuator 30, or some combination of activeand passive forces. Inertial forces will be exerted on the tether 40 asa result of the mass of the A-frame structure 20 and the reflectivemicrostructure 12 that is interconnected therewith, regardless of thedirection of motion of the actuator 30, and are part of the externalforces that are exerted on the tether 40.

[0109] If the magnitude of the external forces exerted on the tether 40are large enough, they can cause the tether 40 to buckle or bend,effectively limiting the total actuation force that may be applied tothe A-frame structure 20 and increasing the time required to move theA-frame structure 20 from one position to another, relative to thesubstrate 100. If the tether 40 buckles or bends, it may act similar toa leaf spring, bending in response to the applied external force andstoring elastic energy which may be reapplied to the system in abacklash situation, an oscillatory situation, or both. A backlash occurswhen the actuator 30 begins moving back toward its static position andthe tether 40 buckles but does not initially lower the A-frame structure20. Once a sufficient force (i.e., elastic energy) is stored in thetether 40, the tether 40 will lower the A-frame structure 20 in anuncontrolled slapping manner, possibly causing damage to one or moreportions of the MEM optical system 10. In addition, any bending/bucklingof the tether 40 may produce mechanical oscillations of the tether 40.These mechanical oscillations may be produced by the above-notedbacklash, by the manner in which the actuator 30 accelerates (positivelyor negatively), by a combination thereof, or by external forces fromanother source(s).

[0110] In order to address the backlash and oscillation problems, it maybe desirable to use a tether 40 that is stiff enough to withstand thecompressive restoring forces exerted thereon without flexing to anundesired degree, including when moving the A-frame structure 20. Ingeneral, slender columns, such as the tether 40, may fail in response tocompressive forces by buckling. The compressive force required to beginbuckling of a slender column (i.e., buckling force) is defined byEuler's formula:

F_(B)=(_(π) ²EI)/L²

[0111] where F_(B) is the greatest force a slender column may withstandwithout buckling, E is the column's modulus of elasticity, I is themoment of inertia across the beams transverse cross-section (e.g.,I=bh³/12 for a rectangular cross section), and L is the length of thebeam. The force produced by the actuator support springs 56 may bedescribed in some instances by Hooke's law:

F_(S)=kx

[0112] where F_(S) is the stored restoring force of an elongated springstretched over a distance x with the spring constant of k. Accordingly,the actuation force exerted on the tether 40 to move the same and thebuckling force of the tether 40 may be expressed in common terms (e.g.,micro-newtons, μN). In order to prevent buckling in the tether 40 (e.g.,to produce a stiff tether) the tether's 40 minimum buckling force,F_(B), should be at least as great as the “x” component of the largestactuation force that will be applied to the tether 40 to move the tetherand the A-frame structure 20 interconnected therewith. Consider the casewhere the tether 40 is formed from a single level of polysilicon havingcross-sectional dimensions of 2 μm height by 10 μm width and a length of1600 μm. Here the expected buckling strength, F_(S), would be around 4μN. Now consider that a typical actuator support spring 56 or that theactuator 30 can otherwise actively deliver an actuation force to thetether 40 in the “x dimension” that may be well over 20 μN. In thiscase, the tether 40 having the above-noted dimensions would buckle.Generally speaking, the desired buckle strength for the tether 40 (whereits buckle strength is at least as great as the “x component” of theactuation force exerted on the tether 40 to purposefully move the tether40 and the A-frame structure 20 interconnected therewith) may berealized by increasing the moment of inertia (e.g., increase the width,the height, or both) of at least a portion of the tether 40 in anappropriate manner.

[0113] One way to increase the buckle strength of the tether 40 when atleast part of the MEM optical system 10 is fabricated using surfacemicromachining techniques, is to define the tether 40 from a pluralityof structural layers. The tether 370 of FIG. 8 utilizes such aconstruction, and may be utilized by any of the above-noted embodiments.Generally, the tether 370 is defined by at least two structural layers372 (372 a and 372 b in the illustrated embodiment) that are disposed invertically spaced relation, and that are rigidly anchored to each otherby a plurality of interconnections 374 that are typically spaced alongthe length of the tether 370. Any way of rigidly interconnectingadjacent structural layers 372 of the tether 370 may be utilized and ina manner so as to attain a desired magnitude of stiffness or bucklestrength between its opposite ends. Although the structural layers 372a, 372 b, and interconnections 374 may be formed from “spaced-in-time”depositions in a surface micromachining process, no “joint” of any kindwill be evident in the resulting structure since the structural layers372 a, 372 b, and interconnections 374 are typically formed from thesame type of material in a surface micromachining process. That is, thecoupling 370 will appear to be an integrally formed structure at leastat some level.

[0114] When a tether 40 is utilized that has a sufficient stiffness towithstand the “x” component of the largest actuation force that isexerted on the tether 40 for purposes of moving the A-frame structure2—from one position to another (e.g., the restoring forces of theactuator support springs 56 (i.e., F_(B)≧F_(S))), the response time ofthe optical system 10 may be improved. Stated another way, utilizing astiff tether 40 maximizes the transmission of the actuation force to theA-frame structure 20, whether this actuation force is “passivelygenerated” (e.g., via the potential energy stored in the actuatorsupport springs 56), “actively generated” (e.g., by providing anactuation signal to the actuator 30), or by a combination thereof. Forexample, a sufficiently stiff tether 40 allows the tether 40 and,therefore, the A-frame structure 20 and reflective microstructure 12, tomove in unison with the actuator 30 when the actuator's 30 movable frame36 begins moving from one position to another. Therefore, increasedswitching speed of the MEM optical system 10 may be accomplished byusing stiffer actuator support springs 56 such that they supply anincreased and, therefore, quicker actuation force to the A-framestructure 20 and reflective microstructure 12 when a voltage is changedacross the actuator combs 32, 34. In one embodiment, switching timesshort than about 20 milliseconds may be realized through use of such astiff tether 40.

[0115] One way to integrate tether 40 having the above-noted stiffnessis by compliantly attaching one of or both the movable frame 36 on theactuator 30 and the A-frame structure 20 to the tether 40 so as to allowthese structures to move relative to one another as the A-framestructure 20 moves relative to the substrate 100. Accordingly and asshown in FIG. 2, the first end 41 of the tether 40 is attached to theA-frame structure 20 by a compliant member 43 and the second end 42 ofthe tether 40 is attached to the movable frame 36 of the actuator 30 bycompliant member 44. As described above, in accordance with the flexiblemember 72 used for attaching the elevation members 22 to theirrespective anchor points 70, compliant members 43 and 44 may be formedsuch that they have a moment of inertia about their bending axes that issubstantially less than the moment of inertia of the tether 40 about thesame axes. This relatively lower moment of inertia in the compliantmembers 43 and 44 substantially isolates bending to the compliantmembers 43 and 44 when the tether 40, A-frame structure 20 and movableframe 36 move relative to one another during operation of the opticalsystem 10. It should be appreciated that the length of the compliantmembers 43, 44 need not be small compared to the length of the tether40. Moreover, members 43, 44 and the flexible members 72 may beconfigured so as to contribute to the actuation force to move theA-frame structure 20 from one position to another.

[0116] The way in which a tether generally of the above-described typeinterconnects with an elevation structure generally of theabove-described type may have an effect on the operation of apositioning system in a microelectromechanical system that utilizesthese types of devices. Various ways of establishing thisinterconnection are illustrated in FIGS. 9-14. The positioning systems378 et al. illustrated therein may be used for any appropriateapplication (e.g., to move any appropriate microstructure byinterconnecting the same with the elevation structure 382 in anyappropriate manner), including without limitation for use in place ofthe positioning systems 18-19 of FIG. 1.

[0117] One way of establishing the noted interconnection is illustratedin FIG. 9 for the case where surface micromachining is used to define atleast a positioning system 378 of a microelectromechanical system.Generally, such a surface micromachined positioning system 378 isdefined in one or more of four vertically spaced structural levels,namely a Poly1 level 402, a Poly2 level 404, a Poly3 level 406, and aPoly4 level 408 (an appropriate sacrificial material having been removedfrom between each of these structural levels in the release of themicroelectromechanical system by exposure to one or more releaseetchants). The positioning system 378 includes an elevation structure orlever/lever assembly 382 that is interconnected with an actuatorassembly 464 by an elongate coupling or tether 400. The actuatorassembly 464 includes one or more actuators of any appropriate type formicroelectromechanical applications, and may be directly or indirectly(e.g., through a displacement multiplier of any appropriatetype/configuration) interconnected with the tether 400.

[0118] The elevation structure 382 is formed in both the Poly3 level 406and the Poly2 level 404 in the case of the FIG. 9 embodiment. In thisregard, the elevation structure 382 includes a pair of lower legs 394 a,394 b that are defined in the Poly2 level 404, a pair of upper legs 386a, 386 b that are defined in the Poly3 level 406 and that appropriatelyanchored to the corresponding lower leg 394 a, 394 b, and a cross member390 that is also defined in the Poly3 level 406, that interconnects theupper legs 386 a, 386 b, and that is disposed at/defines a free end 392of the elevation structure 382. The elevation structure 382 is movablyinterconnected with a substrate 380 on which the microelectromechanicalsystem is fabricated. This movable interconnection is provided by a pairof compliant flexures 396 a, 396 b that are formed in the Poly1 level402 of the microelectromechanical system. Generally, each compliantflexure 396 a, 396 b is less rigid than the elevation structure 382 toallow the free end 392 of the elevation structure 382 to be moved awayfrom the substrate 380 by a flexing of the compliant flexures 396 a, 396b. One portion of each compliant flexure 396 a, 396 b is appropriatelyanchored to its lower leg 394 a, 394 b of the elevation structure 382,while another portion is attached to a corresponding anchor 398 a, 398b. Both anchors 398 a, 398 b extend down to and are attached to thesubstrate 380. Generally, the elevation structure 382 may be of anyconfiguration and formed in one or more of the levels 402, 404, 406, and408. One advantage to forming the elevation structure 382 in multiplelevels 402, 404, 406, and 408 is that different portions of theelevation structure 382 may be configured to have different momentsand/or may be reduce the total amount of force that needs to be exertedon the elevation structure 382 to move the same away from the substrate380.

[0119] The elongate coupling or tether 400, which may be at leastgenerally of the above-described type in relation to enhanced stiffnessor rigidity, extends between and interconnects the actuator assembly 464and the elevation structure 382. The tether 400 is defined in both thePoly3 level 406 and the Poly4 level 408 to provide a desired degree ofstiffness. That portion of the tether 400 that is defined in the Poly3level 406 is attached to that portion of the tether 400 that is definedin the Poly4 level 408 at a plurality of spaced locations along aportion of the length of the tether 400 (not shown in FIG. 9, but seethe FIG. 12 embodiment to be discussed in more detail below). Any way ofanchoring the Poly4 level 408 of the tether 400 to the Poly3 level 406of the tether 400 may be utilized.

[0120] The tether 400 is indirectly interconnected with the elevationstructure 382 in the FIG. 9 embodiment by a connector 412. The connector412 is formed in the Poly4 level 408. That portion of the tether 400that interfaces with the connector 412 is also formed in the Poly4 level408. The connector 412 is defined by a frame 416. Members of this frame416 include a pair of at least generally longitudinally spaced and atleast generally laterally extending connector ends 424 a, 424 b, and apair of at least generally laterally spaced and at least generallylongitudinally extending flex links 420 a, 420 b. As such, the connectorends 424 a, 424 b are disposed at least generally transverse to thetether 400, while the flex links 420 a, 420 b extend at least generallyin the same direction as the tether 400. The end 410 of the tether 400is attached to the connector end 424 b. Where surface micromachining isused to define the positioning system 378 and where the connector 412and the portion of the tether 400 that interfaces with the connector 412are both formed in the Poly4 level 408 as in the case of the illustratedembodiment, there will not be a joint of any kind between the connector412 and the tether 400 (i.e., connector 412 and the portion of thetether 400 that is defined in the Poly4 level 408 will be integrallyformed or of one-piece construction). In any case, the other end 424 aof the connector 412 is attached to the cross beam 390 of the elevationstructure 382 at least at one location, and more typically by pluralityof laterally spaced anchors (not shown). The flex links 420 a, 420 b ofthe connector 412 function as pivot joints by flexing about an axis thatis at least generally transverse to the links 420 a, 420 b duringmovement of the tether 400 via the actuator assembly 464.

[0121] When the tether 400 is placed in tension by a movement of theactuator assembly 464 that is at least generally away from the elevationstructure 382 so as to move the free end 392 of the elevation structure382 at least generally away from the substrate 380, both of the flexlinks 420 a, 420 b of the connector 412 are also placed in tension.Conversely, when the tether 400 is placed in compression by a movementof the actuator assembly 464 that is at least generally toward theelevation structure 382 (e.g., in the opposite direction to theforegoing) so as to move the free end 392 of the elevation structure 382at least generally toward the substrate 380, the flex links 420 a, 420 bof the connector 412 are also placed in compression. In the event thatthese compressive forces exceed a certain level, the flex links 420 a,420 b may flex between the connector ends 424 a, 424 b. Although thismay be desirable in one or more respects, this may adversely affect oneor more aspects of the operation of the positioning system 378. Forinstance, the configuration of the connector 412 may limit the magnitudeof the restoring force that may be exerted on the elevation structure382 by the actuator assembly 464 (through the tether 400 and theconnector 412) to move its free end 392 back toward the substrate 380,and thereby may reduce the frequency response of the positioning system378. Although this may be acceptable in some applications, it may not befor others.

[0122] Another way of interconnecting the tether 400 and the elevationstructure 382 is illustrated in FIG. 10. Those components of the FIG. 9embodiment that are also used in the FIG. 9 embodiment are identified bythe same reference numeral. A “superscript” designation means that thereis at least one difference between the corresponding components of theembodiments of FIGS. 9-10. The tether 400 is indirectly interconnectedwith the elevation structure 382 in the positioning system 378 ^(i) ofFIG. 10 embodiment by a connector 428. The connector 428 is formed inthe Poly4 level 408, and includes an at least generally laterallyextending connector end 432, a pair of at least generally laterallyspaced and longitudinally extending flex links 436 a, 436 b that extendfrom the end 432 at least generally toward the free end 392 of theelevation structure 382, and a pair of interconnects 440 a, 440 b thatextend from their corresponding flex link 436 a, 436 b to theircorresponding leg 386 a, 386 b. As such, both the connector end 432 andthe interconnects 440 a, 440 b are disposed at least generallytransverse to the tether 400, while the flex links 436 a, 436 b extendat least generally parallel to the tether 400.

[0123] The end 410 of the tether 400 is attached to the end 432 of theconnector 428 and is formed in the Poly4 level 408. Where surfacemicromachining is used to define the positioning system 378 ^(i) andwhere the connector 428 and the portion of the tether 400 thatinterfaces with the connector 428 are both formed in the Poly4 level408, as in the case of the FIG. 10 embodiment, there will not be a jointof any kind between the connector 428 and the tether 400 (i.e., theconnector 428 and the portion of the tether 400 that is defined in thePoly4 level 408 will be integrally formed or of one-piece construction).

[0124] The connector 428 is attached to the elevation structure 382 bythe flex link interconnects 440 a, 440 b. These flex link interconnects440 a, 440 b are disposed above their corresponding leg 386 a, 386 b ofthe elevation structure 382 and are appropriately attached thereto by aone or more anchors. Based upon this configuration and manner ofinterconnecting the tether 400 and the elevation structure 382, the flexlinks 436 a, 436 b of the connector 428 function as pivot joints byflexing between their corresponding interconnect 440 a, 440 b and theconnector end 432 if sufficient forces are exerted on the connector 428.

[0125] When the tether 400 is placed in tension by a movement of theactuator assembly 464 that is at least generally away from the elevationstructure 382 so as to move the free end 392 of the elevation structure382 at least generally away from the substrate 380, the flex links 436a, 436 b of the connector 428 are also placed in tension and a torsionalforce may be exerted on each of the interconnects 440 a, 440 b.Conversely, when the tether 400 is placed in compression by a movementof the actuator assembly 464 that is at least generally toward theelevation structure 382 (e.g., in the opposite direction to theforegoing) so as to move the free end 392 of the elevation structure 382at least generally toward the substrate 380, the flex links 436 a, 436 bof the connector 428 are also placed in compression and a torsionalforce may be exerted on each of the interconnects 440 a, 440 b (in anopposite direction to the first noted instance). In the event that thesecompressive forces exceed a certain level, the flex links 436 a, 436 bof the connector 428 may flex between the connector end 432 and theircorresponding interconnect 440 a, 440 b. Although this may be desirablein one or more respects, this may adversely affect one or more aspectsof the operation of the positioning system 378 ^(i). For instance, theconfiguration of the connector 428 may limit the magnitude of therestoring force that may be exerted on the elevation structure 382 bythe actuator assembly 464 (through the tether 400 and the connector 412)to move its free end 392 back toward the substrate 380, and thereby mayreduce the frequency response of the positioning system 378 ^(i).Although this may be acceptable in some applications, it may not be forothers.

[0126] Another way of interconnecting the tether 400 and the elevationstructure 382 is illustrated in FIG. 11. Those components of the FIG. 9embodiment that are also used in the FIG. 11 embodiment are identifiedby the same reference numeral. A “superscript” designation means thatthere is at least one difference between the corresponding components ofthe embodiments of FIGS. 9 and 11. The tether 400 is indirectlyinterconnected with the elevation structure 382 in the positioningsystem 378 ^(ii) of FIG. 11 embodiment by a connector 444. The connector444 is formed in the Poly4 level 408 and is defined by an at leastgenerally rectangular frame 446. A pair of interconnects 460 a, 460 battach the frame 446 to the corresponding upper leg 386 a, 386 b of theelevation structure 382. In the illustrated embodiment, theinterconnects 460 a, 460 b are disposed at a longitudinal midpoint ofthe frame 446 (i.e., half-way between a pair of longitudinally spacedconnector ends 448 a, 448 b) and are each disposed along a commonreference axis. However, the interconnects 460 a, 460 b may be disposedat other longitudinal locations along the frame 446, including where theinterconnects 460 a, 460 b are disposed at different longitudinallocations. Moreover, the interconnects 460 a, 460 b could be orientedother than along a common reference axis (e.g., in offset relation) orother than transverse to the tether 400.

[0127] The frame 446 includes a pair of longitudinally spaced and atleast generally laterally extending ends 448 a, 448 b as noted, and apair of laterally spaced and at least generally longitudinally extendingflex link assemblies 450 a, 450 b. The flex link assembly 450 a includesa pair of flex links 452 a, 452 b, while the flex link assembly 450 bincludes a pair of flex links 452 c, 452 d. The flex links 452 a, 452 bof the flex link assembly 450 a are disposed on one side of the tether400, while the flex links 452 c, 452 d of the flex link assembly 450 bare disposed on the opposite side of the tether 400 (i.e., the flexlinks 452 a, 452 b are laterally spaced in relation to the flex links452 c, 452 d). Preferably, the tether 400 bisects the frame 446 in thelateral dimension, although such need not be the case. In any case, theflex link 452 a extends from where the interconnect 460 a merges withthe frame 446 and the connector end 448 a, while the flex link 452 bextends from where the interconnect 460 a merges with the frame 446 andthe opposite connector end 448 b. Similarly, the flex link 452 c extendsfrom where the interconnect 460 b merges with the frame 446 and theconnector end 448 a, while the flex link 452 d extends from where theinterconnect 460 b merges with the frame 446 and the opposite connectorend 448 b. As such, both the connector ends 448 a, 448 b and theinterconnects 460 a, 460 b are disposed at least generally transverse tothe tether 400, while the flex links 452 a-d each extend at leastgenerally in the same direction as or parallel to the tether 400.Although the flex links 452 a, 452 b are disposed along a common axisand the flex links 452 c, 452 d are disposed along a common axis in theFIG. 11 embodiment, such need not be the case.

[0128] The end 410 of the tether 400 is attached to the connector end448 a of the connector 444, and the tether 400 is also attached to theconnector end 448 b of the connector 444. The portion of the tether 400that interfaces with the connector 444 is formed in the Poly4 level 408.Where surface micromachining is used to define the positioning system378 ^(ii) and where the connector 444 and the portion of the tether 400that interfaces with the connector 444 are both formed in the Poly4level 408 as in the case of the FIG. 11 embodiment, there will not be ajoint of any kind between the connector 444 and the tether 400 (i.e.,the connector 444 and the portion of the tether 400 that is defined inthe Poly4 level 408 will be integrally formed or of one-piececonstruction). The connector 444 is also attached to the elevationstructure 382 by the interconnects 460 a, 460 b. These interconnects 460a, 460 b are disposed above their corresponding upper leg 386 a, 386 bof the elevation structure 382 and are appropriately attached thereto bya one or more anchors.

[0129] When the tether 400 is placed in tension by a movement of theactuator assembly 464 that is at least generally away from the elevationstructure 382 so as to move the free end 392 of the elevation structure382 at least generally away from the substrate 380, the flex links 452b, 452 d of the connector 444 are placed in tension, the flex links 452a, 452 c of the connector 444 are placed in compression, and a torsionalforce may be exerted on each of the interconnects 460 a, 460 b. Thistorsional force may place a tensile force on each of the flex links 452a-d. Conversely, when the tether 400 is placed in compression by amovement of the actuator assembly 464 that is at least generally towardthe elevation structure 382 (e.g., in the opposite direction to theforegoing) so as to move the free end 392 of the elevation structure 382at least generally toward the substrate 380, the flex links 452 b, 452 dof the connector 444 are placed in compression, the flex links 452 a,452 c of the connector 444 are placed in tension, and a torsional forcemay be exerted on each of the interconnects 460 a, 460 b (in an oppositedirection to the first noted instance). Having one flex link 452 on oneside of the tether 400 being in tension and another flex link 452 onthis same side of the tether 400 being in compression, whether thetether 400 is in compression or tension, improves upon the manner inwhich the forces being exerted on the tether 400 are transferred to theelevation structure 382.

[0130] Another way of interconnecting the tether 400 and the elevationstructure 382 is illustrated in FIG. 12. The embodiment of FIG. 12 issimilar to the embodiment of FIG. 11. Those components of the FIG. 12embodiment that are also used in the FIG. 12 embodiment are identifiedby the same reference numeral. A “superscript” designation means thatthere is at least one difference between the corresponding components ofthe embodiments of FIGS. 11 and 12. There are two main differencesbetween the positioning system 378 ^(ii) of FIG. 11 and the positioningsystem 378 ^(iii) of FIG. 12. One is that the connector 444 ^(i) isformed in the Poly3 level 406 in the FIG. 12 embodiment, versus in thePoly4 level 408 in the case of the FIG. 11 embodiment. That portion ofthe tether 400 ^(i) that is formed in the Poly3 level 406 is attached toboth ends 448 a, 448 b of the connector 444 ^(i) by an integralconnection for the illustrated surface micromachined configuration.Another difference is that the portion of the tether 400 ^(i) thatinterfaces with the connector 444 ^(i) is formed in both the Poly3 level406 and the Poly4 level 408 in the case of the FIG. 12 embodiment,versus only in the Poly4 level 408 in the case of the FIG. 11embodiment. That portion of the tether 400 ^(i) that is formed in thePoly3 level 406 is also anchored to that portion of the tether 400 ^(i)that is formed in the Poly4 level 408 at a plurality of spaced locationspreferably along the entire length of the tether 400 ^(i) in the case ofthe FIG. 12 embodiment by a plurality of anchors 468.

[0131] Another way of interconnecting the tether 400 and the elevationstructure 382 is illustrated in FIG. 13. The embodiment of FIG. 13 issimilar to the embodiment of FIG. 12. Those components of the FIG. 13embodiment that are also used in the FIG. 12 embodiment are identifiedby the same reference numeral. A “superscript” designation means thatthere is at least one difference between the corresponding components ofthe embodiments of FIGS. 12 and 13. There are a number of differencesbetween the positioning system 378 ^(iii) of FIG. 12 and the positioningsystem 378 ^(iv) of FIG. 13. A number of these difference relate to thetether 400 ^(ii) and how the same interfaces with the connector 444^(i). Initially, the only point of attachment of the tether 400 ^(ii) tothe connector 444 ^(ii) of FIG. 13 is at the end 448 a of the connector444 ^(i) (which is at/close to the end 410 ^(ii) of the tether 400^(ii)), namely via a tether anchor 472. That is, the tether 400 ^(ii) isnot anchored to the connector 444 ^(ii) at its end 448 b. Anotherdifference is that portion of the tether 400 ^(ii) that is formed in thePoly3 level 406 terminates prior to reaching the end 448 b of theconnector 444 ^(ii). Stated another way, that portion of the tether 400^(ii) that is formed in the Poly3 level 406 is disposed in spacedrelation to the end 448 b of the connector 444 ^(ii). Finally, theconnector 444 ^(ii) includes a center beam 464 that extends between andthat is attached to the ends 448 a and 448 b of the connector 444 ^(ii).This beam 464 is vertically spaced from the overlying tether 400 ^(ii).Once again, since the entirety of the connector 444 ^(ii) is formed inthe Poly3 level 406, there will not be any discernible joint between thecenter beam 464 and the ends 448 a, 448 b.

[0132] Another way of interconnecting the tether 400 and the elevationstructure 382 is illustrated in FIG. 14. Those components of the FIG. 9embodiment that are also used in the FIG. 14 embodiment are identifiedby the same reference numeral. A “superscript” designation means thatthere is at least one difference between the corresponding components ofthe embodiments of FIGS. 9 and 14. The tether 400 is indirectlyinterconnected with the elevation structure 382 in the positioningsystem 378 ^(v) of FIG. 14 embodiment by a connector 500. The connector500 is formed in the Poly4 level 408 and is defined by an at leastgenerally diamond-shaped frame 502. A pair of interconnects 508 a, 508 battach the frame 502 to the corresponding upper leg 386 a, 386 b of theelevation structure 382. In the illustrated embodiment, theinterconnects 508 a, 508 b are disposed at a longitudinal midpoint ofthe frame 502 and are each disposed along a common reference axis.However, the interconnects 508 a, 508 b may be disposed at otherlongitudinal locations along the frame 502, including where theinterconnects 508 a, 508 b are disposed at different longitudinallocations. Moreover, the interconnects 508 a, 508 b could be orientedother than along a common reference axis (e.g., in offset relation) orother than transverse to the tether 400.

[0133] The frame 502 includes a pair of at least generallylongitudinally extending flex link assemblies 504 a, 504 b. The flexlink assembly 504 a includes a pair of flex links 506 a, 506 b, whilethe flex link assembly 504 b includes a pair of flex links 506 c, 506 d.The flex links 506 a, 506 b of the flex link assembly 504 a are disposedon one side of the tether 400, while the flex links 506 c, 506 d of theflex link assembly 504 b are disposed on the opposite side of the tether400 (i.e., the flex links 506 a, 506 b are laterally spaced in relationto the flex links 506 c, 506 d). Preferably, the tether 400 bisects theframe 502 in the lateral dimension, although such need not be the case.In any case, the flex link 506 a extends from where the interconnect 508a merges with the frame 502 to an end 510 a of the connector 500, whilethe flex link 506 b extends from where the interconnect 508 a mergeswith the frame 502 to an opposite end 510 b of the connector 500.Similarly, the flex link 506 c extends from where the interconnect 508 bmerges with the frame 502 to the end 510 a of the connector 500, whilethe flex link 506 d extends from where the interconnect 508 b mergeswith the frame 502 to the end 510 b of the connector 500.

[0134] The end 410 of the tether 400 is attached to the end 510 a of theconnector 500, and the tether 400 is also attached to the end 510 b ofthe connector 500. The portion of the tether 400 that interfaces withthe connector 444 is formed in the Poly4 level 408. Where surfacemicromachining is used to define the positioning system 378 ^(v) andwhere the connector 500 and the portion of the tether 400 thatinterfaces with the connector 500 are both formed in the Poly4 level 408as in the case of the FIG. 14 embodiment, there will not be a joint ofany kind between the connector 500 and the tether 400 (i.e., theconnector 500 and the portion of the tether 400 that is defined in thePoly4 level 408 will be integrally formed or of one-piece construction).The connector 500 is also attached to the elevation structure 382 by theinterconnects 508 a, 508 b. These interconnects 508 a, 508 b aredisposed above their corresponding upper leg 386 a, 386 b of theelevation structure 382 and are appropriately anchored thereto.

[0135] When the tether 400 is placed in tension by a movement of theactuator assembly 464 that is at least generally away from the elevationstructure 382 so as to move the free end 392 of the elevation structure382 at least generally away from the substrate 380, the flex links 506b, 506 d of the connector 500 are placed in tension, the flex links 506a, 506 c of the connector 444 are placed in compression, and a torsionalforce may be exerted on each of the interconnects 508 a, 508 b.Conversely, when the tether 400 is placed in compression by a movementof the actuator assembly 464 that is at least generally toward theelevation structure 382 (e.g., in the opposite direction to theforegoing) so as to move the free end 392 of the elevation structure 382at least generally toward the substrate 380, the flex links 506 b, 506 dof the connector 500 are placed in compression, the flex links 506 a,506 c of the connector 500 are placed in tension, and a torsional forcemay be exerted on each of the interconnects 508 a, 508 b (in an oppositedirection to the first noted instance). Having one flex link 506 on oneside of the tether 400 being in tension and another flex link 506 onthis same side of the tether 400 being in compression, whether thetether 400 is in compression or tension, improves upon the manner inwhich the forces being exerted on the tether 400 are transferred to theelevation structure 382.

[0136] Although the various connectors presented in FIGS. 9-14 have beendescribed as being fabricated in certain of the levels 402, 404, 406,and 408, these connectors may be formed in any one or more of the levels402, 404, 406, and 408 and still provide on or more advantages.

[0137] The foregoing description of the present invention has beenpresented for purposes of illustration and description. Furthermore, thedescription is not intended to limit the invention to the form disclosedherein. Consequently, variations and modifications commensurate with theabove teachings and the skill or knowledge of the relevant art arewithin the scope of the present invention. The embodiments describedhereinabove are further intended to explain best modes known forpracticing the invention and to enable others skilled in the art toutilize the invention in such, or other, embodiments and with variousmodifications required by the particular applications or uses of thepresent invention. It is intended that the appended claims be construedto include alternative embodiments to the extent permitted by the priorart.

What is claimed is:
 1. A method for operating a microelectromechanicalsystem that is fabricated using a substrate and that comprises anelongate coupling microstructure interconnected with a levermicrostructure, wherein said elongate coupling microstructure comprisesfirst and second coupling ends, said method comprising the steps of:accelerating said elongate coupling microstructure; compressing saidelongate coupling microstructure between said first and second couplingends during at least a portion of said accelerating step; moving saidfirst lever end relative to said substrate in response to saidaccelerating step, wherein said moving step is at least substantiallysolely controlled by external forces that are exerted on said elongatecoupling during said accelerating step.
 2. A method, as claimed in claim1, wherein: said accelerating step comprises moving an actuator assemblymicrostructure relative to said substrate, wherein said actuatorassembly microstructure comprises at least one actuator microstructure.3. A method, as claimed in claim 1, wherein: at least a portion of saidaccelerating step is due to inertial forces.
 4. A method, as claimed inclaim 1, wherein: said moving step comprises moving said first lever endalong an at least generally arcuate path.
 5. A method, as claimed inclaim 1, wherein: said moving step is within a first reference planethat is at least substantially perpendicular to a general lateral extentof said substrate.
 6. A method, as claimed in claim 1, wherein: saidexecuting a first moving step is within a first reference plane that isdisposed other than in perpendicular relation to a general lateralextent of said substrate.
 7. A method, as claimed in claim 1, wherein:said accelerating step comprises exerting a force on said elongatecoupling structure microstructure having a component in an x directionof at least about 20 μN, wherein said x direction is parallel with ageneral lateral extent of said substrate.
 8. A method, as claimed inclaim 1, wherein: said compressing step comprises at least substantiallyprecluding storage of any potential energy in said elongate couplingmicrostructure.
 9. A method, as claimed in claim 1, wherein: said movingstep comprises forming said elongate coupling microstructure with abuckle strength between first and second coupling ends of said elongatecoupling microstructure that is greater than a maximum magnitude of acomponent of a force in an x direction that is exerted on said elongatecoupling microstructure used by said accelerating step, wherein said xdirection is parallel with a general lateral extent of said substrate.10. A method, as claimed in claim 1, wherein: said moving step comprisesat least substantially precluding flexure between opposite ends of saidelongate coupling microstructure during said accelerating step.
 11. Amethod, as claimed in claim 1, further comprising the step of: moving amirror microstructure relative to said substrate using said moving,wherein said mirror microstructure is interconnected with a portion ofsaid lever microstructure that is movable relative to said substrate.12. A method, as claimed in claim 11, wherein: said moving a mirrormicrostructure step comprises moving said mirror microstructure from afirst position to a second position in no more than about 20milliseconds.